Fischer Future Heat are a bit of a racket and are not recommended. I do not mean to suggest any criminality, but I understand that they go in for hard selling, a bit like double glazing salesmen used to be.
Electric heating is very expensive to run. Using electricity rather than gas could double your fuel bills, especially as you live in an old terraace house. If you are a mid terrace house you would need to have the two external walls insualated, probably internally, maximum insulation in your loft and full double, preferably triple glazing to make electricity anywhere near gas prices.
If you did go for electricity the simplets cheapest wayof doing it would be to go out and buy electric radiators for each room and plug them into a socket using a timer plug.
Gas is going to be around for a long time yet. We have just bought an old house where the boiler has been condemned and disconnected and now we are in the house we can see the condition of the rusty randomly sized and distributed radiators, which all date to the 1970/80s are such that the way forward is to strip the whole heating system out and start from scratch - and we are going for a new gas central heating system. In an old house I can see no affordable alternative.