Wow, this thread has grown fast!
I couldn't find ANY signage beyond that of the pay-and-display bays; not only, the three other people in my car couldn't find any either (one being my Italian cousin, who even looked when I parked there - especially when I confidently said "you can park on single yellow lines on sundays and after 6:30..." she didn't believe me so she had already looked when we arrived)
That said, Camden is one large controlled zone - so I'm pretty sure that if I were to contest it I would be told that there is a sign two roads down saying I'm entering a controlled zone.
In addition to which, I'm leaving Friday to go on holiday - all in all, I feel quite "annoyed" (to be diplomatic) and don't think its very fair - but its less hassle to pay the £50 than to contest it.
Live and learn...
Thanks for the replies,
Michele
P.S. I will include a letter with my cheque stating how unfair I feel that stretch of road is, and that under slightly different circumstances I would have contested it...