NJ has made a lot of valid points. In particular that employers would need to provide HSE-compliant equipment (such as desktop computers, monitors correctly-adjusted for angle and height, proper office chairs etc) but
(a) the relevant unions will probably do a great deal to ensure that this actually happens ; and
(b) the costs of providing such equipment would be peanuts to, say, a firm who can give up expensive office space in the City of London.
While he's correct in pointing out that people who work from home might face additional heating costs over the winter though, I feel that such costs are unlikely to impact too highly on WFH employees. They'd only amount to a few pounds per day, which could easily be saved by preparing meals at home, rather than buying lunch in Pret, Costa or local takeaway shops, as most office-based workers seem to do.
Against that there could be far larger savings in travel costs. For example, Ipswich is a major commuter station, with loads of packed commuter trains leaving for London every morning. Just parking at the station costs £1994 per year, with a season ticket to London (including Tube travel to an office anywhere in Zones 1 to 6) priced at £8012 per year. So that's £10k in travel costs saved to start with, with fuel costs driving to and from the station needing to be added onto that.
A few hundred quid possibly added to home heating costs isn't going to seriously bother someone who's saving over ten grand a year in travel expenses (and, at the same time, is avoiding having to spend over 20 hours per week in commuting time).