Adding seats to a Vaxhaul Movano

Hi there, wonder if anyone can help. I have a coverted 2004 MWB Vaxhaul Movano. It only has two seats in the front and we have a growing family with a 3 year old and our second due in July. I want to get a double bench seat put in the van preferably with isofix but am having trouble finding someone to do it in Cornwall. Have talked/seen 4 different van convertion people who say it’s not a problem but then fob me off onto someone else they know, which is very frustrating. I’m at a point now where I’m considering sourcing the seats that I think will fit and calling round garages and fitters till I can find someone to put them in, but would really appreciate any advise or recommendations. I live in Cornwall, and just want it done ASAP so we can use the van as a family. Thanks.