The biggest thing to check is that any comoany that operates these tyoes of services ate operating legally, that any minibus is licenced to carry passengers otherwise you will not be insured so yiu should always ask the question and look for the permits, which should be displayed on the fornt of the vehicles
Obviously if you are being collected in a vehicle with a UK number plate there is a problem
Also check insurance status while you are on a trip if it involves any active sports type activities