As has been said, much easier with a License (I managed a couple of years ago), without, much harder. Apart from Boultbee, there is
Spitfire Flights - this is the only setup I have seen that actually offers flights, (Boultbee still operates
AFAIK doing conversions for already licensed pilots). There are also the Grace Spitfire and Anthony Hodgsons that you can enquire about (
Spitfire Flights - Anthonys link on this no longer seems to work, not sure if it is wrong or he is no longer operating it).
Good luck