Warning: MTB’s being stolen out of vans at service stations is a very real thing - I’ve heard several stories of people returning from bike park wales, and having bikes nicked out of van whilst stopped at services on way home. Possibly targeted at bike park car park and followed.
A good friend of mine uses his work LWB transit Kombi van for taking bikes to the bike park, and the cargo section has full bulkhead between it and rear seats. He always purposefully reverse parks with back of van against a wall or something static so that the rear doors can not be opened. He had 3 bikes nicked out of the back of his van at a services on M4….. didn’t even realise the were gone til he got back to Bristol, as thiefs had somehow unlocked the front doors, released hand brake, rolled van forwards, removed bikes, put van back and locked all doors leaving no obvious sign of entry.
Yes your bikes will be safer in a van, but leaving them locked in a van overnight/hours at a time unattended is a very bad idea….. especially a £70k LWB van that shouts expendable income, and a taste for outdoor activities. You may as well have a sticker on the back window that says “£20k’s worth of bikes inside, please don’t steal them”