Thanks for all showing so much interest in the thread.
As i mentioned in the OP, the sound was that of a branch creaking in the wind, but in a short burst, no more that 1-2 seconds max.
I've been around and heard many'a fox, this animal had clear markings and a feline shape.
To my knowledge foxes have mainly a scream or bark? (...i'm happy to be corrected).
I've seen Ocelots in South America and it wasn't that browny colour or as thin.
The closest thing that i've seen after trolling the internet is the 'Andean Cat'. Obviously i'm not suggesting that it is one, but just to paint a clear picture so people stop thinking there's a tiger loose in Surrey!