Becky, here's a starting point, a place between Edinburgh and Glasgow. Mostly sport tourers like a Triumph 955i or Suzuki Bandit, prices from 69 Pounds to 90/day(although it looks like weeklies are discounted some)
AdMo
and here's one with a B&B included:
Bed, Breakfast and Bike
and one more...
rentamotorcycle.uk