Bear wrote:
Luckily my tumble dryer (once purchased) can sit aside an external
wall in the utility room. Question is, how do I bore a hole through
the wall of reasonable size? I'm handy with a drill, but the last
vented dryer I saw required a hole around 6 - 9 inches in diameter!

Chain drill it. IOW drill a series of small holes in a circle of the
appropriate size, then break out the middle with a bolster & hammer.

--
Dave - The Medway Handyman
www.medwayhandyman.co.uk