To me it doesn’t really sound that bad if I’m honest but if you are evading their phone calls and such-like than I’d say it’s surely more hassle than it’s worth and you should just phone them to sort it.
I’m going to be honest and say that if it was me, and the furniture was from some massive department store I don’t think I’d lose any sleep over it.
Though for £600 you’d have to expect them to chase it up sooner or later.
Edit to say that I think suggesting the OP has ‘gone bent’ for £600 (lolz) is a bit much. It’s not like he’s ditched his job to organise a people trafficking ring or something.