starting from scratch, I’d recommend pretty much anything by Coopers depending on the style you’re after.
more help at http://www.jimsbeerkit.co.uk
You’ll also need a fermenting bin, or two; a paddle, hydrometer & trial jar, siphon tubing and enough bottles to put it all in when it’s finished. If your Fermenting Bin lid has a hole, fit a rubber grommet & an airlock to keep the nasties out (wild yeats, vinegar bacteria, and many other things that love beer but make it unpalatable to humans)
If you don’t have a local homebrew shop (LHBS) then Tesco Direct are doing the Coopers Microbrewery which contains everything you need to get started; if you do have a LHBS then please use them, they really do need your support
Finally, cleanliness really is next to godliness when it comes to brewing. clean everything that’s likely to touch the beer, then make sure you give it a REALLY good rinse. yeast & bleach don’t make happy bedfellows
Finally, you need somewhere warm to brew it and do the secondary fermentation (in the bottles, makes it fizzy), somewhere cool to store it for at least two weeks after the above has finished, and LOTS of patience. Kit beers can take up to 2 weeks to ferment depending on temperature, plus 2 weeks in the warm for the secondary fermentation, and another 2 or more weeks in the cool for bottle conditioning.
do NOT keep peeking in the fermentation bin, you’ll let the nasties in