I sold my Sub 4 for £350 a few weeks ago, just remember with your price that it's a buyers market and the fact you can get a decent condition Warwick Corvette 5 standard for £450 if you look in the right place.
Also with mine I found the colour would sometimes look black (I had the blue one) do you ever find this? Very nice SUB though, I will always have a soft spot for them since my old one.