Managed to locate and purchase a set of new door locks and keys, and new ignition barrel and keys for the 'Tin Tent', at very reasonable prices. My usual mechanic bloke will fit these, after gaining access to the vehicle, asap.
Thankfully, the battery is dead at the moment, so at least the thieves who burgled my house, taking the keys, can't actually take the van - unless they have a tow truck that can lift it over my neighbour's car !