We also looked at a holiday in the Western Isles this summer - we love the area- but 10 days of independent travel plus b+bs would be IRO ?800 for two adults and one child - totally prohibitive. Getting a ?59 Eurostar ticket to Paris is a little more attractive and holds more promise of a good time than staying in the UK. The only thing I would rate highly for comfort and value is the Youth Hostel Association and thats probably the way forward for us in the UK. .
Paris I love, but you'll be lucky to manage 10 days there on ?800 for 2 adults + child. And no lochs or mountains in sight