So you are going to be moving to this lovely island of ours
I am afraid that as you probably know crafting does not seem to be as big here in England as it seems to be in the US!
I'm afraid I hadn't heard of Poynton but I have looked and it seems to be in Cheshire??? Is that the one? I don't know that area myself as I am in Leicester which is in the midlands but I am pretty sure one of the lovely gals on here will be able to help you out with regards local shops and events etc.
There are no 'chain' type fabric stores in the UK like you seem to have JoAnn's etc. They tend to be local shops or local chains, I think there is one in the North, have a look through this England board and you should find mention of it.
Car boot sales seem to be everywhere (in Leicester anyway) so there are some treasures to be found I am sure, these are usually just advertised locally and on sign posts and such. As for estate sales we don't tend to have too many of those, in fact I have never heard of any, there are people that do House Clearance as a business but that type of thing isn't advertised to the general public. There are a lot of charity shops in the UK so you might be able to find some stuff there.
Blimely this is getting long sorry, yeah guys aren't too useful about know about fabric unfortunately
If I was you I would definately bring as much fabric as you can, there seems to be lots more variety for you guys (after looking at US websites) here the choice is limited.
I hope this helps a little, I am sure the rest of the UK gals will help you out with other ideas, this was all i could think of at the minute!
Good luck and keep us posted with the progress!