No ones being a cock, if you had bothered to look around before you put your advert up you would have known there was a great community spirit here, an appraisals section and this thread.
Just putting up a random number is not going to win you any favours and hopefully not going to get you any interest or sales. This thread is here for the regulars to have some lighthearted banter about wishful thinking like your original listing. A lot of the time advertisers like yourself make their way into here and either throw their toys out of the pram or take things on board like you have.
Based on the value and the extras (admittedly not worth a great deal extra to 70% of buyers) I would say asking for £200 like you have changed it too is more realistic but I would expect to pay about £150 TOPS as that is about 60% value of the total costs new.
And not a personal dig but WTF is wrong with the world if throwing up a random number thats double what something cost onto any sort of advert/marketplace? is this really the accepted norm on bookface? bloody hell!!