In reply to George Fisher:
I can add more later, but leaving it until August will massively increase available accommodation. Most Swedes, plus a lot of Danes holiday from mid summer through to the end of July.
Trains are cheaper than uk anyway, buy a family ticket. 2 adults and 2 kids travel for less than the cost of two singles.
Edit. Leave it past mid August and some tourist places will be winding down as the kids start back to school. (They finished school this and last week).
Post edited at 17:26