If going for a new connection I'd recommend going to Topcashback, Quidco, Hotukdeals or Compare the Meerkat for some very good deals and check the reviews.
Rated best to worst:
Hyperoptic: Excellent speeds and very good customer service
Zen: best service, very rarely drops out, great router, just initially pricey and may include hidden fees or different prices on the phone to their website.
Plusnet: Good but regular disconnections and waited a month just for them to cancel an installation
BT: Most of the time okay but a nightmare when you have problems
Virgin: Dropouts once a month and speeds aren't as advertised. They may still be oversubscribed.
Sky: Avoid, many dropouts, bills doubling in price for no reason
TalkTalk: From one of my neighbor's experiences 10 years ago I would say no, but maybe things have changed since.
Take a pinch of salt with any reviews site: