Is there anything I need to be aware of signing up from the UK, perhaps re print labs, deliveries, shipping etc.
Everything on SmugMug just "works" from the UK, so there's really no difference right now. We just added the ability to buy in your local currency, so you'll find GBP in the shopping cart now. Today, prints and gifts will be fulfilled by our US Labs. But soon that will change. It's the #1 feature request on our feedback forum and it's not being ignored.
When using any of our US Labs, printing is rather fast, but it does ship across the pond.
EDIT: SmugMug announced that UK and EU Customers will be served by Loxley Colour starting on March 23, 2012.