Hi Jamie
Flush mount hole required is 149mm x 61.6mm
Manual says front dimensions164x78mm approx 150 mm deep but add another 20mm depth for cooling space
Added the template photo on eBay listing.
I’m hoping eBay bid to be around 110 quid.
Happy to let sell it cheaper to a Ribnetter for £90 inc postage if you make a donation to the RNLI