@TheArcher thanks for the suggestion, but that actually is pretty much the "business model" I utilise. I get batches of manuals printed in anticipation of demand. However as this is at my own personal expense, I like to get an idea of demand before ordering fresh batches, as I need to have a minimum of 10 manuals printed per batch in order to get a reasonable price. I'm doing this as a service, not to make a profit (which isn't allowed on the forum anyway), so, understandably I hope, don't want to tie up too much of my own money in unsold manuals.
The manuals do have a fixed price, which is:
Owner's Manual £9.67 + £2.69 postage + £0.38 packing = £12.74
Navi Manual £4.63 + £2.69 postage + £0.38 packing = £7.70
Both Manuals £9.67 + £4.63 + £2.99 postage + 2 x £0.38 packing = £18.05
I will be receiving another batch (10) of SatNav/Infotainment manuals tomorrow (5 Jan) so I'll have up to 4 Owner's manuals and 8 SatNav/Infotainment manuals available then