You submit an application form, an illustration of the design and the registration fee to the Intellectual Property Office. The Intellectual Property Office does not conduct a search of registered designs as part of the process, but will tell you if they think there are problems with the novelty of the design. All being well, registration usually takes two to four months. The whole process is relatively simple, though you may want to use an agent if you expect your registration to meet with objections.
The application fee is currently £60 (but only £35 for textile designs). After five years, you pay a renewal fee of £130 if you want to maintain registration, and increasing renewal fees for subsequent five year periods up to the 25 year limit.