Guys for your info.
Meng do a nice range of plastic Nuts and bolts and a few conical rivets too with and without washers in about 6 different sets.
The small sets range from 0.8mm upto 1.7mm, the large from 1.8mm to 2.5mm and you get more than plenty of each on a sheet of snap off tabs.
thers also sheets of allen socket heads and recessed nuts you could drill the centres through.
Very innovative
Hannants have them in stock, just search under nuts. or bolts...

Keith