I dont know about old radio valves but I do know about guitar amplifier valves (the same things!)
There are obviously loads of different ones but if youve got any mullards and they say anything like EL84, 6V6, ECC83 or 12AX7, youll sell thme very easily providing theyre all working
You might be better off going to someone like Hot Rox or the tube store who may take the lot for a decent amount – save you faffing with ebay and fees and postage (but stay away from Watford Valves – the worst reputation Ive come across, The Dave Hinde of the Valve World!)
On the other hand Ill give you say £20… 😉