If it's kits you want then google Velleman quite a range with plenty of soldering. Maplin used to stock them but I think you can order directly off their website. Some of the component suppliers who specialise in the education market like Rapid Electronics stock them. However, the kits rarely educate you in electronics and you will have to resort to book learning if you want to gain any understanding. There are a few online sites which will get you started as well as online libraries of circuits.

If you want a good book with practical exercises then I can recommend Michael W Brimicombe, Introducing Electronic Systems ISBN 0-17-448068 but the most useful is the accompanying Introducing Electronic Sytems Practicals which is a ring binder of worksheets that accompany the book ISBN 0-17-448161-6.. Both these were published in 1987 and are probably out of print but if you can find them second hand I think you will find them . useful getting started. If you can find someone who has the worksheets they are easy to photocopy as they are all single sided sheets, try the DT dept. of some of your local schools. Failing that contact Nelson who were the publisher.

As Brain has said many of the kits now contain a PIC or other custom chip that does most of the grunt. If you want to get into Microcontrollers can I recommend the PICAXE system as a quick and easy way to get into them and how to program them, software and manuals are all FREE (I always like the sound of that word) and a helpful forum go to www.picaxe.co.uk.

Good luck
Richard