Now checked. Obviously there are a lot of variables but they might offset a bit eg
I have a terraced house (which should by rights be warmer than a semi because no heat-leaking end wall at one side) but on the other hand, it's big (17/18 ft ceilings in the hall and 14 foot in the main ground floor rooms) and I would guess might be bigger than yours, being Victorian rather than Edwardian. (7 or 8 rooms plus halls, bathrooms, kitchen etc.)
I kept my heating on through the day (and night) at times this winter because it was so bitter compared to last year - but I keep the setting mostly at 16 degrees.
(I'm not going to get into competitive coldness here. 18 is quite a reasonable temperature for you to go for. There's a school of thought which says that if you keep your heating on a lower setting permanently, it's cheaper. I can't get my head round the science of that (temperature gradients and all) but I was certainly much relieved by the winter bills after putting the heating on 'ON' for weeks on end, albeit on a lowish setting, and with a price rise of - 10% I think it was.)
Anyway, my total winter quarter (gas, electricity and VAT) was somewhere just south of £630 compared to your £955. Admittedly, we've got heavy loft insulation and are seriously economical with energy use that we don't need. (eg lights are turned off and rooms not being used at any point have the doors closed, the radiator thermostats turned right down and heavy curtains pulled.) Nonetheless, the windows are single glazed, original and drafty. (They actually rattle in the slightest wind.) The (conventional) boiler is about 7 years old but pretty efficient according to the engineers - who didn't even try to sell me a new one on the last visit.
I'd be looking at further energy saving if I were you. I'd also be having a serious talk with the family about whether you actually want to move. (It's hell going from a roomy house to one which is not so roomy - but also any prospective purchasers will likely want to know about energy bills if you decide to sell.) If you can get on top of it, that should benefit you either staying or leaving.
Sorry for the tome.