Just to bring everyone up to date - the drug doesn't seem to have made any difference to me at all. My RLS has its own routine, it hits me for 3-4 nights then I get one or two nights off - they're just rough estimates. So I'm back in the RLS phase but it's no worse or better than it's ever been.
I won't give up on the drug now (prescribed for fibromyalgia pain) as my GP has assured me that hopefully within a month of starting it I should feel much better.