Virgin Media Business offer SLAs etc. When I switched from consumer to business it actually cost just slightly less, and there's no in-contract price increases. Of course, if you want an email service, you are out of luck, but you can have a static address with a PTR record to run your own.
Having said that, it can still take an age to get something fixed, but at least you have a proper customer service person to complain to - on the consumer side the customer service is truly appalling.
If I had a decent alternative (my phone line under the ground is aluminium and noisy as hell, so I am stuck with cable) I'd move. The first company to make me a good FFTP offer will probably win.