What brilliant answers and food for thought you've all given me.
To answer some questions, yes I think it will be really hard to downsize so much, we don't just have 3 bedrooms we also have 2 offices, 3 reception rooms, a massive shed and a garage. We're thinking about this as a short term move 5-10 years and I appreciate what you all say about the areas and how they hold their value.
We're interested in having some fun, going out a lot to theatres etc. We can easily move jobs to Central London, we have a lot of interests and hobbies we can easily do from there.
Our families are still out here and we would still keep the garage for storage plus we own a field with a shed on it that we can store tools etc rather than getting rid of everything. We would have a lot of stuff to get rid of and I do think it would be tough to live somewhere so small.
I would love a terrace and there's a few flats I've seen that have that or a balcony.
The flat in kennington is in the Wellington Mills development, not incredibly attractive but not awful looking.
I'm also really glad that you've said how safe these areas are, I've walked round them all and they certainly feel safe as their so central.
They are all crazy expensive places to live, for £350-£400k you get if you're lucky a 10ft by 8ft bedroom, living room same size, teeny kitchen and shower room