Replacing built in under-workstop oven with larger unit

I'm at my mum's for the weekend and her oven died on her yesterday, so we picked up one on ebay this morning.

The old unit was a single oven, built-in, under-worktop. The new one is also under-worktop, but a double oven.

I've removed the old oven which leaves the following hole:

By my measurements, the new oven will be flush with the plinth, so even if I could take the shelf out and refit it to the base of the unit, it would still be half an inch too high. (The new oven is 72cm high).

I've tried to remove the housing unit to remove the shelf, but it's far from straightforward as the plinth is welded into place and there's a risk of breaking it in removing - also the pipe to the gas hob (which also needs replacing - not by me!) is in the way.


My thinking is I could smash out the shelf - if I'm careful I'll leave it largely intact - then cut the depth down on it so that it fits behind the plinth and pick up 4 legs so I end up with the shelf free-standing on the ground at the right level for the oven. I can then leave the rest of the work for the electrician to do after the plumber has sorted out the new hob.

What I'm unsure of is whether a free-standing shelf as described would be ok for the new oven, but I can't see any other way of fitting it into the existing space. How would a 72cm high oven normally fit under a worktop?

Thoughts?