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A lot of 60s houses were built with fireplaces as central heating was still a bit of a luxery. In 1970 only 30% of houses had central heating rising to 59% in 1980 and 79% in 1990.
As the ever fascinating @mespilus mentioned somewhere on here recently mains (North Sea) gas only came along between the late 60s and mid 70s. Before that it was coal (town) gas which was stored in gasometers and piped around your house via those thick old steel gas pipes sometimes found when renovating older houses (I pulled a load out when we redid our flat).
I had no idea mains gas was such a modern thing until he posted that!
You bought a house without being sure what era it was even from?
Ballsy.
https://www.oldmapsonline.org/en/Manchester ?
A 60s house could well have floorboards but they would look different to Victorian floorboards which are quite distinctive. One reason for this is that due to the Victorian building boom there was a pine shortage, so a lot of pine was shipped over from Canada. Working out what sort of pine you've got might therefore shed some light.
I also suspect some 60s houses were built with fireplaces. You'd be better off looking for distinctively Victorian building methods but it might just be easier to look at old maps and see when your place first existed.