I live in London. I am not a teacher. Some thoughts:

• London is a special case. Teacher salaries in London are higher than outside of London to reflect the higher cost of living. I don't know if your research has factored this in. I am not personally very knowledgeable on the subject of teacher salaries, but know a few. Teachers themselves are, for obvious reasons, highly knowledgeable about teacher salaries.

• "London" covers a large area. All of it is relatively expensive compared to the rest of the UK (and the world), but £26,000 would get you a lot further in, say, Croydon than one of the more central boroughs. Also a lot of places get called "London" by faraway folk when they're not. If your job is in Basildon or Reading or some other orbital town, those places aren't London, either culturally or expense-wise, and you'd want to adjust your queries accordingly.

• £24,000-£26,000 does seem startlingly low to me (a software developer in his thirties who solves problems by throwing money at them), but by way of comparison, a starting police officer earns ~£22,000, so it's presumably not an utterly ludicrous amount.

• We have different rates and brackets of income tax to the US. £26,000 translates to £20,634.72 take-home pay. Your first £10,000 is untaxed, 20% thereafter until you hit the mid-thirties.

• The biggest expense of London by at least one order of magnitude is rent. The second is transport. Minimising these expenses is an obvious way of stretching your budget, but there are sharp trade-offs in terms of location and travel costs. Public transport in London is expensive but a lot cheaper than running a car, and actually very good compared to every other town and city I've lived in (sample size 5, all British). We have a lot of cyclists, but it's not really a city optimised for cycling.

If you were to join the Less Wrong London group, we have a pretty good track record of advising people considering moving to the city.