Thans for all the comments guys - I appreciate it.
Doobie - great tip! Only thing is I glued the sleeper on yesterday so I don't have access to the inside (@#$%^*&.......) I just went out and had a look and yes it looks like poo with the clear windows and white interior (can't believe I didn't notice it before).
I think I'll try and 'smoke' up those widows somehow with varnish or nail polish or something - any tips?
Apart from that it's pretty much finished, just got to put the ac unit on and 'plumb' it.