It seems that the problem is related to the hogging of bandwidth by the various MyHobbyStore shops (must be doing well for Christmas!)
A couple of solutions have been looked at with marginal improvements, but Katy the web master has made this announcement today:
"We are hoping to move the magazine websites to a new server without the shop websites this week. I'm hoping this will help with the speed issues. We have some testing to do first, but I will let you know when we're going ahead"
Fingers crossed.
Neil