There's an urban myth that if you go into any big supermarket and ask nicely at the bakery counter they'll happily give you a lump of fresh yeast. I've never met anyone who'd done this, and I don't have the nerve to try it. But I've found a much more expensive way of getting fresh yeast, which does at least work.
The Bertinet Kitchen Cookery School sells it online. Price is £3.95 plus postage of around £3 for a block of 500 grams. I imagine the cost is all to do with the preparation and that the wholesale price is a lot less. I ordered on Tuesday, the yeast was dispatched on Wednesday, I received it about 10 on Thursday, and by 2 pm I had this cooling on the table:
The yeast variety is Hirondelle, which is what my very local baker, Cooper's Bakehouse, uses. There it's described as "a slow-acting, gentle yeast". I probably used too much yeast, as it rose very quickly, but it's an impressively light half-wholemeal loaf. Next time I'll use less and give it a longer rise, so that the flavour develops better.
But I'm very pleased and I now have enough fresh yeast to last me a few months. Some is still in the fridge, and I've frozen quite a bit of it in manageable lumps. It arrived in good condition in a huge amount of thermal insulation.
So, if you want fresh yeast, this is something you could try. 500g is a hell of a lot for a home baker, though, so I'd suggest if you can find someone to share with, do.