After some real soul searching and grown-up thinking I've decided to be smart and sell this wonderful thing.
My reasoning goes as follows:
I'm 42 and self-employed. With that comes a constant underlying sense of anxiety of advancing age, staying busy with work and keeping everything financial nice and safe. I have some savings, but not enough that I could cover things for more than a few months of down time. Also, in the future, I'd quite like to go out on my own and have my own shop...that requires capital. Despite what my buying habits might imply, I'm not a wealthy person, it's mostly good luck and a little bit of skullduggery
I'd be a LOT better if I could get to a stage that I have some proper "fuck you" money if I need to bounce from something for whatever reason.
If I keep it I have some serious bragging rights, a cool story and a fun guitar. If I sell it, all I lose really is the bragging rights, and I don't really care about that, and I still have great guitars. It turns out I value longer term financial and mental stability over this guitar. With the sale from this I can pay for a solid chunk of our Japan holiday, pay off the last few installments on the car, treat myself to something cheap-ish and save the rest (which will still be a lot).
I've made my decision. I have a potential buyer already that's hopefully coming Tuesday.
Let's see.
What a ride.
Let's hope further numbers that come back are more sensible. £500 I could probably stomach, £850 is daylight robbery IMHO.
...I guess London prices and all that, but still...I too would be comfier around the £500 mark. 
