Yes a IMC is useful, not so much as a teaching aid but allows you to fly in weather with lower margins and then recover to your departure airfield. However this wont be appreciated if you continually fly a 20 min procedure in your students time.
Try Aeros at Gloucester 01452 857419 and
www.aeros.co.uk for the FI course as Gloucester is an excellent GA field.
cheers
MJR