Here in Taunton the situation is (at the bakery counter):
ASDA give it away; Sainsbury's sell 800g for £2.29 (used to be 99p not long ago) or 50g for 19p; Morrison's will tell you it's in the chiller cabinets - but it never is! And Tesco, who used to give it away, now don't want to know.
Strong bread flour is currently 77p a bag in Sainsbury's and 60p in Morrison's. I never bother with branded flours, don't see the knead (sorry!)
Edit: Forgot to say, if you can't get fresh yeast, dried active yeast is the next best. Allinson's is readily available at 64p a tin - right by the flour shelves. Don't bother with the sugar and waiting ten minutes as the instructions would have it - once it's dissolved in warm water, it's ready for use.
It'll last for ages - once opened, keep it in the fridge.
I don't use the fast action stuff for two reasons - firstly it costs up to 3 times more than the dried active, but, secondly it's only about 93% yeast. The rest comprises 'additives' and enzymes and therefore is not recommended by the Real Bread Campaign.
Many years ago I used to get lumps of yeast given to me by the bakers in Tesco, sometimes for nothing, sometimes for perhaps 20p. My difficulty with that was that I would end up wasting a fair bit of it and feeling guilty, so I switched to the dried stuff.
I've used Dove Farm fast acting dried yeast for years with total success -- never had any problems or concerns about it. A pack of 125g costs 99p in Waitrose and lasts me a month or more.
That said, I am attempting to get a sourdough culture going and with any luck I'll be able to use that for a lot of what I bake.
I have also found supermarkets to be "hit and miss"....I think it depends on your local store. I've always found small bread shops with their own bakery more than welcome to sell a fair quantity of fresh yeast to you for no more than 20p......especially if you catch them at a quiet moment and say you are an amateur baker.
I have also found that the dried active yeast is the best of all the dried sachet options.
I use fresh yeast from Sainsbury, Asda stopped selling it to me, I've never tried Tesco.
I haven't used it myself, but my mother swears by Fermipan. It's dried yeast, but comes in a big 500g vacuum packed block and can be found in most health food shops or online. Lasts really well and is good value for money.
I'd rather use fresh yeast every time, no particular reason, I just prefer it.
my local Morrison's won't even sell it, local Sainsbury will sell it for 50p for a decent chunk so no complaints from me, the flour is the killer cost.
How is flour the killer cost, unless you are conned in to buying "Extra Strong Bread Flour" at a premium price? Even then, it is still cheaper to make your own than to buy ready made bread. Any flour over 12% protein will produce decent results if you are free shaping loaves. If using a bread tin, the cheap own label stuff, with around 10.6%-11% protein, works well enough for me.
You can raise the protein content of inexpensive flour yourself. I have tried this and it works well enough, but I can't say the difference is great enough to excite me. You can buy 80% protein, the stuff used to make seitan, online. It's not cheap, but you need only add a couple of teaspoons full (about 15g, less than 10p worth) to 500g of flour to raise the total protein levels by a couple of percent (2.4% if you want to be pedantic).
I have also learned to be less trusting of labelling, since meeting a supermarket worker who used to work in a flour mill. He told me that the same silo was used to fill the bags of an expensive branded flour as for a supermarket's own brand flour at less than half the price. This, despite the cheaper version being labelled as having a protein content 2% lower than that of the premium brand.