I would say "I really enjoy travelling by campervan", we usually use 'by' when we are talking about a mode of transport. It is possible to say "Last year I travelled across American in a campervan", here you need the article 'a' before campervan. I hope this helps. Emma - Talk2Me English

'By camper van' is an adverbial phrase, similar to 'by car' by plane' or 'on foot'. Because these are set phrases, they are seen as single grammatical units with their own internal grammar - hence the lack of article and lack of plural form.So: 'We really enjoy travelling by camper van' is fine. If you use 'in', you are not using a set adverbial phrase, so you need to use standard grammar for the nouns. 'We really enjoy travelling in a camper van' is grammatically correct, but it is something which we would in fact be very unlikely to say. More likely statements would be the following: . 'We really enjoy travelling in our camper van' (our own vehicle) . 'We really enjoy travelling in camper vans' (camper vans in general - this has a similar meaning to 'by camper van'.) . 'We'd really enjoy travelling in a camper van' (Conditional - a statement about one hypothetical trip). I hope that makes sense - please feel free to ask if it's not.