I'd also love to rely on brick and mortar stores. There are SO few in London it is quite a shock. However, I've found one closer to where I live - it was closed on Sunday can't wait for the weekend to go see if it is any good.
One other store I found on my journey in to work, apparently is closed Monday and half day Wednesday, is only open from 10am to 5pm and closes for an hour at lunchtimes. They could not guarantee it would be open on Saturdays either =(
I need a good source of yarn that delivers to the UK!