145x10 makes me think of the old 'Mini' wheel and tyre, which has a 4 inch pcd.
Just checked this on the towsure.com site and all their 145x10 tyres fitted to new wheels are a 4" pcd, which kind of confirms what I was thinking. There's loads of good info on their site which you can access without buying. Locally, Port Sunlight Trailers sell a lot of the Towsure items, and they are friendly helpful people as well.
(Before anyone says it, other sizes af rims, tyres and PCD's are avaliable)