The thing is - these are public buildings and not spending what is allocated results in decay etc and can cost far more in the long term. From your link:
No 10 has confirmed that the full £30,000 grant for upkeep of the living accommodation, which is available to prime ministers annually, was used for the refit of 11 Downing Street, after the Guardian discovered the payment in the official spending records.
A spokeswoman said the money was spent on rewiring, plumbing and decorating but insisted the Camerons paid for the extras. "No public money was spent on furniture, fittings or accessories," she said
The other £653,192.34 was spent on external and internal renovation of the offices and reception rooms in Downing Street, including cabling, plumbing and energy efficiency improvements.
I understood the Camerons paid for the hi-tech kitchen themselves - which will be there for the use and enjoyment of future PM of whatever persuasion.
Didn't the Blairs take over the flat of No 11 because it was larger and they were expecting baby No 4? I wonder how neglected that was too. They obviously didn't spend much of the £1 million {shock] on rewiring and essential maintenance!
^Mr Blair's written parliamentary answers say the expenditure is "mainly attributable to the refurbishment of the state rooms and coverting the top floor of the building into office accommodation."
The answers estimate spending on wallpaper at approximately £1,200.
Mr Blair's close colleague, the Lord Chancellor, Lord Irvine, was widely criticised for spending £650,000 upgrading his official residence last year.
None of them have heard of Ikea or B&Q