My understanding is that it is, if you are looking at a newer one.
Pre 2001 they are all about £230.
Post 2001 the TD5 CSW costs £280 up till about March 2006, then rises to £500. After 2011 it's £220 as they were reclassified as commercial vehicles.
The hard top is classified as a commercial vehicle so is £220 across the board.
So l would say go for a pre-March 2006 CSW (or a hardtop and convert it to a SW which costs around £1,000)