After a lot of messing about and phoning and emailing the IoM I managed to get two three day reservations on the Island.
The first was a recommendation from one of the places I phoned and is at Ballaugh. I took and address and sent a deposit to them ages ago. I should really check my cheque book as I've not had a receipt from the lady I spoke to, nor a reply to my letter asking for directions. The Cronk at Ballaugh seems too vague!
The second place is at Foxdale. They did send a receipt and a nice map.