the splash back doesn't have to sit hard against the wall and follow the walls chase, the only issue will be a varied gap at the top if the walls are that far out.
I used glass in my last PPOR and will probably be putting it in when i renovate my IP given the cost versus ease of cleaning between tenants. Worst they can do is either crack it entirely (bond/insurance) or not clean one line of silicon. Versus the grey area of white grout no longer being white grout.
We have just used Stegbar (Jeldwen) to do ours. It was arranged through their Sunshine Coast agency. 6mm toughened, ionised glass (won't crack with heat and doesn't give 'green' tinge to whatever backing colour you choose) was cut in Melbourne and freighted to Hervey Bay.
Approx 3.8m length x 330mm high in total across two pieces, with 3 x GPO cut outs and 900mm riser from gas cooktop to below rangehood about $1360.00??? from memory.
We looked at other options but because it is our PPOR we went with the glass. Had a look at laminates etc. but it looked sh#thouse.