Jane, I had very low pressure this morning too (in Halifax Street). My boiler seemed to be working ok so I thought it must be a more general problem. Thanks for letting us know.
We had no cold water this morning (Westwood Hill) and I rang Thames Water before 8.00am. I too was told there was a problem up at Crystal Palace/Gypsy Hill. It also caused a big traffic jam, I think it was a burst main. Its back on now though.