Sync speeds won't be affected, anything the ISP is responsible for could potentially slow you down.
I am on a discounted package with BT at the moment anyway so I'm not in a hurry to break contract and go elsewhere, if you don't have an issue with the price then the actual product is decent.
Same.
I've just had the email regarding the price increases, and have been given the option to keep the current price if I re-sign for another 18 months. It's a no-brainer in my case.