Do you shop at Tescos? If you use Tesco vouchers they are very cheap, if you don't they're not.
A 4-bed room costs around £50-£70. Some include breakfast, some don't.
The beds, rooms, bathrooms and kitchens are clean. Bedding is fine now too.
Most people do get up early. In most hostels breakfast is 7.30-9.00, and you're likely to hear other people getting up certainly from 7.00.
(Having said that ds2 got up at 6.30 on Tuesday, so I sent him to the lounge in his PJs and went back to bed. We didn't wake up until 8.10 when he came back to ask whether we were going to have any breakfast that day!)
We've never had problems with late night noise, though it can sometimes happen at hostels. But staff will deal with it if there's a problem. Generally IME it's very quiet from 10pm.
Irritating happy/healthy types ..? Well, maybe. One of the things we like about YHAs is how friendly they are: the children all play together and you do swap stories with the other people staying rather than just keeping yourself to yourself. But some people stay quiet, and that's fine.
(I've only stayed in a city YHA once, and I think those may sometimes be less full of happy/healthy people!)
Also for the past 6 years we have lived in a very mono-cultural town, which is a struggle for us at times. We love the fact that at a YHA you generally get people from all over the world and lots of different languages, which is great for our boys especially, who are not used to that.
For us the great bonus is the locations. We like hiking and bird-watching, and being able to walk from the door is wonderful. Then when you get back to the hostel there are always drying rooms for boots and clothes, and it feels luxurious compared to camping.