New oven - clearance to extractor

Aylesbury_Duck

I ordered a new oven online from John Lewis, with installation added. Rangemaster have confirmed a delivery date and sent some pre-installation videos. Before ordering I measured to make sure the new oven would fit. The video guidance states the required clearances around the oven (which mine will meet) but there is an extra requirement in the delivery guidance: There needs to be at least 650mm between the top of the gas hob (measured from the top of the pan supports) and any combustible materials. I have a stainless steel extractor above the existing gas hob but it is only 635mm above the pan supports. The extractor has gauze grease filters, so no combustible filter paper. I rang Rangemaster to find out if it would be acceptable and their technical department said "it should be ok". They suggested the installers "should be pragmatic about it."

Given the above, isn't there a risk that the installer refuses to install the oven? If any gas professionals out there can advise, is my current situation acceptable or not? I'm not disputing the clearance - it's 15mm short - but it's the interpretation of that and the combustible materials requirement that I can't seem to get a clear answer on. If it was a kitchen cupboard 635mm above the hob I can see it would definitely be a non-starter. If there's a problem, I'd rather push back the delivery until I can see if the hood can be moved further up the wall.

Edited to add: Having got home and measured again, it’s worse than I thought. The wok burner in the middle stands higher than the other pan supports, making the clearance only 610mm to the hood. It looks like I’ll have to postpone installation until I can make the necessary alterations to the hood height.