ik9000, I have no idea where you've got your information from but London is losing industrial land at an alarming rate. What you define as derelict sites may well be hosting valuable businesses. My local council and the GLA made a similar mistake when they assessed a piece of land in my local area to host a tram depot as part of the Crossriver tram project. Fortunate for us, a local campaign helped safeguarded local businesses. Now the area is featured regularly in newspapers and magazines as a place to visit.
I fully agree with you about overseas investors buying real estate in London which exacerbates the housing crisis and the proliferation of tall buildings that ruins our skyline. There is the issue of social cleansing in the northern part of my local borough. In fact, social cleansing is happening in other parts of London as well.
Not sure where you got the idea that all councils are against tubes. Currently there is a Bakerloo extension consultation in my local area where the route is likely to pass through two Labour controlled local authorities and one Tory local authority. The Tory local authority is against the idea as it means losing their rail service but the two Labour local authorities are broadly supportive of the extension. I doubt if TfL is considering other tube extensions as all of the lines are full to capacity. However, there is a suggestion that there may be a southern extension to the Victoria line once Crossrail 2 has been completed.
As for stamp duty, I'd like to see its return to its original format. High stamp duty impedes freedom of movement and economic activity. While it's argued stamp duty raises a certain amount of money, the Treasury would have received the money anyway through economic activity in my opinion. The purpose of raising stamp duty was to stop rising house prices but we all know this has failed and the stamp duty thresholds has not kept pace with house price inflation.