Thanks Horse. I should tell you that out single glazed wooden framed windows are being changed to double glazed by replacing all of the casements, so it is possible to conserve energy without breaking the bank. Our dining room window frame was rotten so we had to have the whole thing changed at a cost of approx £2000. Mind, like all the other windows, it had been in place for 50 odd years.
Must say I'm a bit surprised that teak windows need much maintenance - surely a bit of mason's wax every year would do it?