Hello Everyone

Hi there and welcome to the forum. 
I have only been keeping fish for around 18 months, and have found the experience and advice available on this site amazing.
What are your tap water parameters? If you check on you water suppliers website they should give all the information on hardness, etc. This sort of thing can be quite helpful.
Great to hear that you are planning a fishless cycle. 
I quite like the Fluval Roma tanks, and have the 125L and 200L tanks. I find the lids very easy to work with. The U3 filter is quite chunky, but it does the job.
Please keep us updated on your progress, with pics if possible. 

Welcome to the forum!

Thanks for the warm welcome everyone!

The water supplier's website says the pH is 7.6 and Ca is 65.9 mg/l , although it also says the the Water hardness average is 108.9mg/l calcium!

Will this affect my choices?

Thanks Sue - it's Yorkshire Water, but they have different supplies depending on postcode.  I've (hopefully!) attached a screenshot so you can see the data.

My water is even harder than yours at 17dh.
I have mainly stuck with fish that work well in hard water (livebearers, oddballs, etc), but I confess that I have also kept fish slightly outside their normal range. Generally it is best to keep fish in the middle of their preferred range for all water parameters. However, some commercially bred fish are considered more adaptable to a wider range of parameters that their wild counterparts.
I'm choosing my words very carefully here as this can be quite a controversial topic.
In my opinion - which I would like to point out really doesn't count for much as I'm still a relative newbie, and my opinions have also been formed from dealing with living in a hard water region - if you are going to try to change your water parameters you may be better off with mixing your tap water with RO water (easily purchased from fish stores like MA). I have previously tried to use products like "pH down" during my very first fishless cycle. It precipitated out and the whole tanks went cloudy, refused to clear, and had to be stripped down & the cycle started again.
In praise of hard water, it makes your tank very stable, but can direct your choices of stock in the direction of things like dwarf puffers (I love mine) and other quirky characters (I also find my mudskippers endlessly entertaining, like having tiny, finned puppies).
Have a look at this article, as it may also direct you towards fish that you may not have considered, but may be quite similar in shape or colour to those that you like.
http://www.wetwebmedia.com/FWSubWebIndex/fwhardness.htm
On the other hand, and this is where things can become quite controversial, I have fish in some of my tanks that would not be considered suitable for my water conditions. I have fish that are normally listed as the top of their range being perhaps 12dh. I spoke to staff at local stores, and found that they imported their stock from commercial farms that had similar/slightly harder water conditions to our local area. On one hand, that's great, because the fish would be sort of acclimatised to hard water. On the other hand, evolution is not a speedy process, so even if the fish have been bred in water outside their "normal, wild type" parameters for many generations, the associated issues of keeping fish in harder water (shortened life span due to kidney & other internal organ problems) are still valid.
It's a tricky one.
Luckily I'm very partial to weird stuff (puffers, mudskippers, axolotls), most of which are more suitable for hard water. The sewellia linealoata, which I have wanted for ages, are generally only available from wild caught stock (another controversial topic), so the river tank I'm setting up for them is going to be a mix of tap & RO to make the water more suitable for them, as wild stock are better kept more towards the middle of their stated range.
I don't have any fish that would be considered really soft water fish, but I do admit to keeping fish in water that is harder than the top of their stated range.

Can I suggest all male endlers rather than guppies. http://www.seriouslyfish.com/species/poecilia-wingei/ They don't have the long flowing tails that guppies have, and are less likely to get fin-nipped by other fish. Some fish just can't help themselves when they see long flowing fins, and bloodfin tetras are in this group. Endlers may be small but they are brightly coloured which makes up for their lack of size. Endlers in shops are actually endler-guppy hybrids rather than pure endler, and they come in a variety of different colours and patterns.
If you don't mind small fish, how about emerald rasboras http://www.seriouslyfish.com/species/celestichthys-erythromicron/

Brilliant thanks - like the idea of all-male endlers and cherry barbs.  I'm guessing if the endlers are like guppies, they would stay nearer the top of the tank with the barbs occupying the middle to lower half?  They're both pretty small too, which would mean we could get quite a decent quantity of each.  The emerald rasboras are absolutely beautiful, but the 20+ numbers recommended on Seriously Fish would seriously limit how many other fish we could put in the 125l tank, I think.

I have had both cherry barbs and endlers (though with my soft water I should not have had endlers  ). I found the cherry barbs did a lot of grazing from the bottom of the tank looking for tiny bits of left over food, while the male endlers spent most of their time mid level, displaying to one another. Female endlers behave more like cherry barbs but male livebearers have one track minds. The male endlers I had would spend time displaying to each other which consisted of bending their bodies sideways into a curve, flaring out their fins and sort of twitching. They also liked to play chase - a group of them would chase after one endler, then they'd turn around and chase another. But they never made contact or hurt each other.
As for cherry barbs, there is a colour variant in which the males are orange and the females yellow, both with red eyes. I got my albinos from Maidenhead Aquatics.