"It must have been a huge extension"

... says TL (via email), having read this:

"They're from my parents on behalf of the family. It's a thank you for right-to-buy. They bought their council house, a three-bed Victorian in East Dulwich, for £17,000. They've extended it and done a lot of work – we're a family of builders – and it's been valued now at about £1m. It's a policy which changed everything for us." – Samuel Tuck, 40, from East Dulwich, who brought a bouquet of flowers to St Paul's.
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The Daily Mail gets in a couple of observations about land/location values as well:

Joe Walker, 32, a Big Issue-seller from Canada, said he had moved from his usual Regent Street patch to The Strand to take advantage of the increased footfall from the funeral procession(1).

'It seems like people love her and hate her here, and I can see why,' he said. 'It's amazing that people can buy their own council houses in England, it's my dream to own my own house. But then I know some people who take advantage of it and sell them on for much higher prices, so no one can get a home.'(2)

1) Yup. The rental value of land depends (largely) on the number of people/population density. If there are more people on The Strand, then you will sell more newspapers there than on Regent Street for little extra effort. The extra profits you make where there are more people are "rent".

2) Yes, but they had to spend a fortune on improvements and massive extensions first, the real profits weren't that big.