Thank you very much everyone for your input. Had a weekend of renewed searching and have ordered grey metro tiles in the end (the Fired Earth 'Euston' ones with some colour contrast in them) which we're planning to do with a dark-ish grey grout. Fingers crossed it works....
Having seen the photo (lovely kitchen!) I do understand you are after a little colour. Grey or mosaics as suggested would both look good I reckon, you can always add more colour with wall paint, pics, flowers etc.
Graphite grey coloured blackboard paint. 10cm high clear glass for the bottom corner/join with the worktop for water tightness and then a packet of multicoloured blackboard pens...and voila - a constantly changing splashback.
How funny, I was going to suggest marble too, there is a lovely photo in the WHite Co catalogue of a handleless white kitchen with a tall marble splashback, looks great. There is very little marbling in it though, so it looks a lot plainer than in the link above. I think glass does look a little dated, but if you like it pootle then that is what counts!
Ooh thank you - interesting ideas legosaurus! We have a marble topped dining table so I think the first one might overdo it but I do like it. I really like the Popham tiles....had always thought that Moroccan tiles wouldn't go but actually they have a few I really rather like.
Our kitchen has just been fitted and I love it - but we need to sort out a splashback for behind the sink.
The kitchen has worktops and cupboard fronts all made from white Corian - like this http://blog.higham.co.uk/2012/02/times-corian-in-bricks-mortar.html
The area behind the sink is 2m long by about 0.7m high (cupboards either side and above). Because the kitchen is all very white, with white walls and grey floor, I was thinking of something fairly bright to add some colour.
Sheet of glass is easiest to clean but I'm worried it already looks a bit dated. And it is only behind the sink as the hob is on the island. Wondered about glass tiles....there are two options - standard size ones, or bespoke (considerably pricier) so that we can fit the tiles exactly to the space...if doing the latter would have approx 290mm x 98mm tiles and tile them one above the other rather than brick style. With standard size tiles probably 200x100mm tiles done either stacked or brick wall style (which?)
Or any other suggestions? Need to decide soon as everything else is close to being finished.