A Victorian Glasgow tenement flat is a difficult place to heat.

Those huge, beautiful but single-glazed bay windows may be much admired, but they're incapable of blocking out the cold air coming in, or trapping warmth from within. Residents cannot replace them with double-glazing if they're in a conservation area, which creates problems every winter. To add fuel to the metaphorical fire, the stripped original floorboards that are so fashionable become a curse when freezing air blows through the spaces between them.

With heating bills going through the roof, and temperatures plummeting to -7 in recent nights, it's not just tenement dwellers who are revisting the inexpensive joys of the old-fashioned hot water bottle. It has been reported that sales of the rubber hot-water comforters have tripled in the last month compared to the same time last year, and at least one in five of us now owns one. This has given rise to a new line in fashion: the hot water bottle cover. Sales have leapt by over 400%.

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There is an incredible range of styles this year, from folksy Cath Kidson and trendy Hello Kitty, to luxury designer cable-knit cashmere versions with pom-poms. My favourites are the Sarah Lund-style Fair Isle versions from TK Maxx, of which I've purchased several as Christmas presents. There are even microwaveable bottles for those who wish to avoid the problems of burning by hot water.

New research from Anglia Ruskin University has found that if the bottles are poorly made or the rubber has perished, or if you haven't screwed the lid on tight enough, they can explode, causing serious burns or scalds. Even if the water is lukewarm by the time it bursts, the inconvenience of having to change the bed and don dry pyjamas in the freezing cold can be considerable.