yeah bike-art have a fleet of basic hardtails for about £12/hr iirc
look variable quality but dig around and you should find something half decent ( and shouldn’t be too badly trashed as its early in the season)
if you want top-end / full sus phone them and reserve at least 24hrs in advance and take your own pedals
can’t remember rates but i think they were reasonable
customer service not a strong point there though so be prepared for norfolk grumpiness and don’t take it personally 🙁