Hostels are flexible and cheap and many offer smaller rooms of 2/4/6/8 beds. Usually the group would book whole rooms for our exclusive use. Many hostels were former mansions or country-houses and offer clean and modern kitchens and bathrooms. The days of dormitories and slopping out are long gone! The group often uses Youth Hostel Association (YHA) accommodation; non-YHA members may have to pay a surcharge. Try www.yha.org.uk or independent hostel websites for more details. Some hostel reviews can be found at yha.forumsplace.com.
Cottages or chalets offer exclusive quality accommodation and occasionally can be found at similar price per person to hostels. However you have to book the whole cottage or chalet and the number of beds or single beds may be an issue. Great for smaller numbers or if you can find them at good price.
Camping is cheap and ideal in summer for a few days with dry and warm weather. Waking up next to nature and late nights outside talking, eating and drinking. Usually need to book pitches in advance though. Need sleeping bags and maybe ear plugs for those who might not sleep too easy. Basic tents probably fine for UK summer camping unless luxury or more robust (waterproof) features required.
Bunkhouses are usually converted barns etc. Many beds in one or two big areas, separate area to cook, eat and wash in. Cheap but basic. Rarely used by the group but usually perfectly clean and habitable for those who don't mind sharing rooms with possibly lots of others or even in a through room!
Bed and breakfast is flexible, costs more, great for very small numbers. Limited supply. Available all over the country, used occasionally by late comers to weekends or weeks away or by those who want separate living space from the group.
Hotels offer more privacy and higher quality but you pay for it. More likely to use for some of those foreign events that occasionally appear on the program. Can be reasonable price in certain countries around the world.
Sleeping under the stars is last but not least. This can just about be done - but few tend to plan to! Alcohol might be a factor! As long as it's safe and legal then it's ok. Not something that's done very often by the group.