The 'best' ...that's like asking which is the best beer, really it depends on your tastes and what you want out of it more than anything.
Personally, I like mechanical keyboards, these are expensive though compared to the common rubber membrane type. I would tend to recommend a decent quality membrane keyboard to you, rather than a mechanical ...because you would 'know' if you wanted a mechanical keyboard, also you'ed need to be prepared to spend £60+
As a basic but decent quality keyboard I like the Cherry CyMotion Expert
http://www.overclockers.co.uk/showproduct.php?prodid=KB-007-CH&groupid=702&catid=23&subcat=2 ...it's cheap, pretty well made and I personally like the key feel, it doesn't have a load of crap I don't want either, maybe you do though I don't know.
What I would not recommend are the over-priced, over hyped Logitech 'gaming' keyboards with LCD's and such, because as actual keyboards they are quite poor in my opinion and after all you are looking for a keyboard not an lcd right ?
Hewlett Packard's bog standard silver and black desktop keyboard, which you can find for about £8 if you really look is actually quite good for what it is too, the quality of the keyboard is a match for any of the typical gamer aimed stuff but without all the lights and lcd's and macro buttons etc. I don't like it as much as the Cherry but for £8-£10 it's great ...far, far, far better than anything Microsoft or Logitech offer at the price.
All in all though the best keyboards use a mechanical keyswitch design, such as the Filco Majestouch, which is one of the easier ones to get in the UK today. They are around £100 each though. SteelSeries actually do one aimed at gamers too, that's over £100 too. You can get the Filco with different types of keyswitch in though, depending on the tacticle response you prefer.
As for Mice, well ...there are more really good mice around than keyboards, I think until recently 'quality' keyboards have been neglected by the market a lot but Mice have gotten better and better. Mice are very personal things indeed, and you need to find a shape and weight that you are comfortable with, also you need to decide weather you want corded or cordless, I would suggest that for gaming you should stick to corded though really, they are better suited for it generally. Personally, I like the Razer Deathadder, I also use a cordless Microsoft Explorer which I like.