Just received some card ordered monday evening, 25 sheets each of 360 and  600 gsm (0.6mm and 1mm) greyboard which is recycled; it's quite stiff and  reasonable cost  £12.41 including p&p (RM 48hr). Some good discounts  rfor larger quantities, also sheets up to 3mm thick & A1 size.

For N gauge the 0.6mm will be ideal for house walls with the 1mm for larger buildings. The 1mm should also be OK for garden and other walls, also floors and ceilings to help keep buildings square

https://papercutz.co.uk/greyboard-backing-board/greyboard#page=1&top=1081.433349609375&
https://papercutz.co.uk/greyboard-backing-board/greyboard/grey-boards-quick-buy

Looks like a good place to stock up on board.
Thank you for the tip!

Gordon :-)

I like to recycle the off-cuts that picture framers produce in great quantity. I asked politely at my local shop and she provided me a large supply for free.You should be able to get a range of shades, as used in the Barn I built recently (W-H p4).


PS this was a most helpful tip I got from late friend John Flann