I usually get to 30 items by the end of April - though this year it's been a lot harder to sell anything.

I sold well over 100 records last year and the year before that.

You may find it really IS Ebay that's the stumbling block here, as they've added buyer fees and now Simple Delivery, so all your £3 records will need at least £2.72 tracked postage. Making selling them that much harder from a buyer's point of view. Even combining multiple sales to one buyer is a major faff now. And those obstacles have nothing to do with HMRC.

But, as Edwardian says, it's YOUR own stuff, so you are free to sell it all and there are NO tax implications.

Good luck.