TimTW;
Check the requirements in CAP 804 downloadable from the CAA website. I'm afraid it will probably be far more than 3 hours.
When you choose your school take a good look at the experience of the instructors, Rolie James and Dave Arkell at Starspeed will always have my highest endorsement. I dread to think how many IR renewals I have done with Rolie over the years and his knowledge and training methods are outstanding.
SND