I live on the outskirts of London, Tunbridge Wells seems like very much countryside to me, and round here you wouldn't pay much more for a house that size.
Leaving the price aside though, things that leap out to me are
Location - busy road. I'm sure you are far enough back not to get traffic noise but even so I wouldn't want to be on a main road like that.
Plot layout - it's a big plot and lovely garden BUT it's been extended to the limits both sides so to me it feels too close to the neighbours. If I'm buying a detached house I'd want a bit of distance!
Downstairs layout - I'm not a massive fan of total open plan, I like to have a separate lounge with doors, as well as space for table and sofa in/ around the kitchen. So that wouldn't work for me. Also all that op n space would take a huge amount to heat.
Location of the loo - I find it really annoying when downstairs loos are so far from the front door. I like them being either right by the door or under the stairs!
There are not enough bedrooms for the downstairs space in my view, also at least 1 of the rooms has floorboards so I'd have to carpet that.
It's a nice enough house but it doesn't wow me, and certainly for me there would be too many compromises involved. I'd take less space for a 20ft gap either side between me and the neighbours!