What's your problem with BT that is making you wish to change your ISP.?
A lot of folk do Not realise that without BT Telephone Exchanges, very few ISPs could survive. Consequently, if problems arise, it is possible that BT customers take precedence over other ISP customers who are having their Broadband connections via a BT Telephone Exchange.
I admit that I am with BT and remain very happy with its service.