I live in a house with reinforced concrete floors. I can not get a good signal upstairs nor indeed further away than 10-15 metres with my supplied Thomson WiFi router.
What should I look for in a new WiFi router to replace my current one?
I fully agree with Nontek's recommendation. I had the same problem, connecting my wife's PC to the router via wireless. With homeplugs she now has a reliable connection, with almost no loss in speed compared to my PC which is hard wired to the router.
I bought mine from ebuyer where there is a good selection.
Possibly stating the obvious, but if you want wireless in the far rooms, make sure you buy one wired (connects to router) and one wireless home plug (wireless ones are more expensive). An example is here Others are cheaper, but I have had some problems with some of the budget ones.
Nontek - I agree, but he did say he was getting a poor wireless signal. I use a pair of wired homeplugs, then pluged in an old wireless router to the far one as a wireless access point - best of both worlds!