Having looked at a variety of ways to retain a little more heat in the VX cabin I tried a few options and material combinationss and have have come up with a solution. I have had two of these made so fat, one which is fitted to my car and another than Cramman has bought/testing.
They are made to fit directly into the soft top and you have can either double sided tape it to the soft top (for super quick removal of the top on the good days) or fit like have, by draping it of the two support rails, put the soft top on as normal and then tuck it into the corners afterwards. Based on current material costs I am going to offer these for £20 each including postage, initially on just here and vx220.org but will then offer them on eBay (more generally for anyone to buy, but will probably be £40).
From my own personal experience they do make a fairly considerable difference to the amount of heat lost through the soft top fabric, as the materials work together to lock out the cooling draw of the soft top, but as an additional bonus they help cut down the noise from the wind rushing over the fabric at motorway speeds.
These will take a few weeks to sort, so I propose that if anyone wants one, I will take orders until Sunday 14th Nov and will order material and get the person fabricating them on the job as soon as the materials arrive, so all being well the first bunch should be off the sewing machine, packed and posted by the 28th of Nov.
Finally I can offer these with the black liner only for £20, but if you want a different fabric colour just ask and I shall see what I can sort, I know I can get a red or blue tartan (but would be about £10 extra). Additionally the £20 version will be panelled (6 or 8 panels -a bit like feather quilts), but for £5 more I can get them sewn with a diagonal or quilted pattern (see pics below for what I mean).
Pannelled:

Diagonal quilting:

Inside the soft top (as double sided taped in):

How it tucks under the support panels:

As fitted to my car:




List to follow.