Looking at the Walford kit that's about as simple as it gets really. There is the option of the very cheap transistor radio kits from China as well. Not affiliated with the seller here but this is a typical example:
https://www.ebay.co.uk/itm/263408131354
Also to note is the GQRP "sudden" kit here but you'll have to join GQRP club to get it (£6 for membership and thoroughly worth it from experience):
http://www.gqrp.com/sudden.htm
And if you don't fancy that, there are some projects towards the end of the following book which use "canned components" which are easy to get in the UK:
https://www.amazon.co.uk/dp/1905086849
I haven't actually done the intermediate yet myself (literally just did foundation) but from what I've seen they should cover the requirements in theory.