Agree with what @Solgrass said regarding kerb appeal - the first thing I saw was the wires and it put me off.
For all the house you get 600k seems reasonable to me, but others know the area so perhaps heed that.
No floor plan, looks like the garage is yours from pictures but it isn’t.
Kitchen/conservatory is a dream.
Master disaster - I wouldn’t pay £600k to sleep on a mezzanine with the bulk of space below used as a corridor…. Where is the storage?? Is could easily be dressed as a dressing area with storage or as a relaxing area to read or watch tv.
Also, a problem faced by selling when you have children is that the cot/kids stuff immediately marks it as a family space so young professionals or dinks discount it as unsuitable, and people who want to have a family see the cot and think ahh they’re moving it can’t be big enough or isn’t suitable for a family (as they don’t know your personal circumstances with twins/distance from family).
Wishing you all the best of luck, it really is a beautiful house, hopefully you will get a buyer soon with a few tweaks/change of agent.