As
@UnkleSkunk has said, bubble bags just require the bags (cheap on ebay etc.),a few bags of ice and a big (clean) bucket. You could probably get all of this for under 50 quid. If you want to make life easier for yourself, it helps to have a chest freezer, so you can drop the whole bucket in and leave it for a few hours. I don't personally think you need to agitate it so much that you'd need a paint mixer, but it depends how cold you can get the water in the bucket. Less cold = more agitation required (and more plant matter released).
I make BHO (shatter) using butane, an extraction tube, a vacuum pump and a heat mat. All in, I think I paid about 200 GBP including the pump oil, super-clean butane ("Newport Zero Impurities") and everything else, but it's not for the faint of heart and you should not do anything with butane indoors as its dangerous, so you need garden space or similar. Once it's in the vacuum chamber it should be safe to bring inside as the amount of butane remaining it is relatively small.
The absolute cheapest extraction you can do is coconut oil for edibles. When I do this, I de-carb the herb in the oven first, then setup a slow cooker and add in all the de-carbed herb and the unrefined coconut oil together for a couple of hours on a low heat. I then pour everything from the slow cooker through a coffee filter (multiple layers of muslin will also work if you have no filters to hand). You can then use the (now green) coconut oil in place of butter in any recipe you like and you'll have yourself some tasty edibles. It seems to last for months when kept in the fridge.
I've used this method to make everything from gummy bears to hash brownies and they always turn out well. I recommend buying some powdered lecithin to add to your recipes as well, as it makes the THC easier for the human body to digest (i.e. you get higher). If you plan to make gummy bears, you should also buy a mould (under a tenner on Amazon - I have traditional gummy bear shape, Super Mario and Final Fantasy characters etc. - and some malic acid so you can make sour flavours. I took these on a
flight to Japan and they randomly spot-checked my bag at customs but said nothing about my gummies! Highly recommend.