The TSP is a defined contribution 401a plan and part of the Federal Employees Retirement System. It is therefore a US government pension as far as the treaty is concerned.
Well.....if it is.....makes things pretty simple.....
1. My pension and TSP withdrawals would only be taxed in the US.....which makes figuring out how much to take out of the TSP easier to hopefully stay in a lower tax rate.
2. Social Security would only be taxed in the UK, which at todays exchange would put me less than £2,000 over the tax threshold. Of course if the Pound creeps back higher that could keep me at/close to the threshold. Still another 3 years until I need to worry about it.
With this plan I shouldn't have to worry about double taxation.....and reclaiming it on taxes etc. I like things being easy........