The UK offers a wide variety of hotels rated on a scale of stars, from 5-star luxury and beyond! to 1-star basic. There is also a vast number of privately run bed and breakfast establishments abbreviated as "B&B", offering rooms with usually a fried 'full English breakfast'. Alternatively you can rent a private house which is let as a holiday home; many such holiday homes advertise on a wide variety of free websites or advertise on their own websites. Good deals can usually be found by using a search engine for "self-catering holiday accommodation".
Budget travellers can opt to stay in a youth/backpackers' hostel
YHA England and Wales (http://www.yha.org.uk), tel 0870 770 6113
Scottish YHA (http://www.syha.org.uk/), Email - email@example.com, tel 0870 1553255
HI Northern Ireland (http://www.hini.org.uk/), tel 028 9032 4733
In recent years an independent hostel scene has opened up, with some privately owned hostels offering a more relaxed regime than the YHA. They're listed on the Independent Hostel Guide (http://www.independenthos...).
Another option is to stay at short term rental apartments. There are numerous such companies around the country.
There are also many campsites, with widely varying levels of facilities. "Wild camping" on private land outside recognised campsites may be awkward outside remote areas, though one-night camping stops may be feasible if undertaken discreetly, or landowners may give permission to wild-camp for free, or for a small fee, if asked.
Some travellers to the United Kingdom decide on a campervan or caravan holiday, whereby your accommodation travels with you. Most parts of the country have a good range of camping and caravan parks available.
If you are smart enough you can hire a camper, and park in remote pub parking spaces [ask first] and really enjoy the country side atmosphere and unique tiny pubs.
As a more quirky though sometimes expensive option, the Landmark Trust (http://www.landmarktrust....) is a charitable organisation that buys up historic buildings, follies and other unusual examples of architecture - especially those in danger of destruction - and renovates them in order to rent them out to holidaymakers. For bookings, tel 01628 825925, mailto:firstname.lastname@example.org