You should base your decision on who offers you the fastest speed at the exchange your moving to, or who offers you the lowest price. This will obviously depend on your criteria.
Generally speaking the lowest priced options offer the slowest speeds, and vice a versa.
It's not particularly difficult to pick an ISP these days the information is out there
Sky might be the best option for you at the new home, but unless you check the exchange your'e just shoving your finger up in the air and going in the direction the wind is blowing. Also using sites like Quidco and Top cashback and see you net up to £80 just for choosing the ISP you were going to go with in the first place.
It will take two weeks because your phone line will need to be activated first, then you'll need to get ADSL added onto the line. Unless you're a business, you won't have the option of a simultaneous provide, which seldom works anyway. It's just how things go, although often with some nifty phone calls to keep on top of things you can get the connection up and running much faster. The timeframes are usually worst case scenarios, phoning can make people look at the database and push things along to the next phase more quickly. This will obviously depend on what company you are with, and what systems the person in the call centre has access to
Get a 3G dongle in the short term, or pair it with your phone. If you want a quick and easy solution, buy a £25 iPad sim from Three. Use quidco to get £12.50 back for it and bingo you're away. If you dont' have an iPad, you can use the sim in a dongle, by just walking into any phone shop and asking for a micro sim adapter. You'll get 3Gig of data for that, or 3 months of usage, which ever comes first