I can't answer your question as I've never done anything like this, however, I can tell you that if you are using your own milk, the other ingredient prices are essentially negligable. 19 liters of rennet is on the order of 350 GBP. That's enough for 2500 - 3000 kg of cheese. Cultures will run up to 10 GBP for 100 kg of cheese depending on what you are doing. You main costs are going to be capital costs and labour. Well... and waste. There *will* be a percentage of cheese you don't sell.
For soft cheeses, you can probably count on 15% yield from the milk. Then if you target 250 grams per cheese (say for a bloomy rind). Maybe 25p per cheese for rennet and cultures (there are ways to reduce that quite a bit, but let's be conservative). Let's say you do 200 cheeses a week and charge 4 GBP per cheese, that's sales of 800 GBP per week or about 40K per year. It will use up about 330 liters of milk a week. You have to age them for at least 4 weeks, so you need a cave capable of storing 400 cheeses for 2 weeks at 12 C and 90% humidity. Then you need to wrap 200 cheeses a week and store 400 cheeses in a normal fridge for a further 2 weeks. You need to flip those 800 cheeses daily. Also you need to make 40 cheeses a day, 5 days a week. It's basically a full time job... and it will probably eke out minimum wage after all the expenses. Profits go up as you scale up, but especially if you are thinking of less volume, it's going to be pretty hard to make money I think.
On the other hand, you might just consider cheese making an experimental venture that isn't intended to make a profit initially. If you keep the volume down (maybe so that you are only making cheese one day a week), it won't make any significant money, but at least you can test your market.