Help with B&Q oven housing Base Unit?

Hi, I'm trying to install a ceramic hob on top of my oven housing unit, the installation guide specifies a minimum 50mm gap between the hob and the rear wall, with the hob in position, (no worktop installed yet obviously) this gap is only 15mm, no movement forward is possible due to the white plastic bracket that carries the forward metal support bar. Even with the hob sitting In a 3.8cm worktop cutout, there would still not be enough clearance.

Any suggestions on how to proceed, am I...

Help with B&Q oven housing Base Unit?