Thanks for the info! That might explain the lack of response, but I was only going by the latest Purplemarine catalogue [because we bought it with a load of other stuff and I couldn't remember what we bought it for] and it is £139.99 in there.
Having re-read my previous post, I think I ought to clarify. Yes, you can get this on its own for £80, but ours comes with all that is on the Purple Marine website for £140, which includes - dash mount, charging lead and carry case, so on reflection, new price - £80 + post & packing!