How many bedrooms do you need? Is your group a mixture of adults and children? A few years ago we were going to do a similar thing for my mother's 70th birthday, in October. We were thinking of hiring a whole Youth Hostel, (in Ambleside), which means you also have full access to the kitchen. Our party was around 22 (including kids of all ages). If you can find one in a location suitable for all guests then this is a really great, and cost effective option, and many Youth Hostels are in really beautiful areas. Have a look at www.yha.org.uk for more info.