Just to update this, I ordered the deeper battery lid part number 31335286 from volvotradeparts on eBay - £37 inc postage, quite expensive but the best price I could find.
Great service as usual and it arrived in a few days. However, it didn’t fit my battery box as the clips didn’t line up and the front profile as a little different. I sent it back for a refund no problem and have since adopted a more heath robinson approach like Kev with the original lid, but I secured mine with some Velcro straps. Saved £37 and looks fine to be honest
