Exactly as said earlier, set your eBay listings to look at sold prices, but yeah 50p should be worth 50p, if you see the same type sold for more, then fair enough try to get more if you like.
its funny how humans, with the right hype can make absolutely anything desirable, but greed can get the better of everyone, this isn’t me getting at you by the way OP. I’m an 80s kid and I collected garbage pail kid stickers when I was a kid, and of course I stuck them on my bedroom door and they were scraped off when my dad decorated, so I didn’t have any left. As an adult I went on eBay looking for some, I got a few for a reasonable price, but greedy collectors have made a whole industry out of it, it’s ridiculous. Grading their condition then selling them off at a massive profit. I just wanted to look at them/handle them and enjoy the memories, not keep them in an airtight container never to be seen again. There are newer items as well, models etc, I would have loved to own a few, but again they are bought in bulk, graded then sold for huge amounts before someone like me can get even one for retail price.
I collect vintage LPs as well, but I go for the cheaper dog eared ones because I just want to enjoy them. Sorry bit of a rant about the collectors market there, by all means join in and sell it on OP, or release it back into the wild to fulfil its destiny as currency.