Firstly, thank you all SO much for all the help!!
All these suggestions are great ideas, but due to events leading up to the “Lorry scene”, some are more applicable than others (for instance, he has no hope of getting an accomplice!).
The first applicable idea that really appeals to me is Freight Dog and Wiretwister’s roped and sheeted flat bed trailer. I really, really like that idea, because it seems so retro, but I have a further question about it, if anyone could be so kind: Do foreign lorries ever pick up goods in another country and bring them back to their own country?
The thing is, in the story, my lad chose the lorry he got into because it had a Polish registration plate, as he thought, logically, that it would have to go back to Poland sooner or later. But the thing is, if this Polish lorry is in England, I assume the driver would have to deliver his load before he leaves England to go home? So he would either deliver his load in England and find my lad inside (putting my lad back to square one), or the driver would already have delivered his load when my lad finds the lorry, so it would be empty (with no cargo for my lad to camouflage in)?
I also really like Cavey’s car transporter idea – but again, I have the same question. If a foreign lorry is transporting cars, wouldn’t it drop them off in England and then go home empty?
Or, is there another way to tell where a lorry is going without looking at the registration plate? One way, as tonyj105 suggested, is that I build into my story my lad finding a company that exports to Poland, but he really doesn’t have time. He came up with this idea on the fly, and he’s clearly wearing prison clothes. He has to get out of sight ASAP. So, if there is a way to tell where a lorry is headed, it needs to be a quick way!
Thanks again to everyone for the help, I don’t know what I’d do otherwise!!