Any question answered...

are oil filled radiators cheap to run? that is my main concern tbh

no electric heating is cheap to run unless you have an economy 7 or similar tariff. and with them you can only heat at night cheaply with storage heaters etc

Note, the use of the term cheap is a relative one as nothing is cheap anymore. Energy suppliers are taking the piss these days

This.

All portable heaters are shocking. Oil filled slightly less shocking than fan heaters: You may as well make a fire with crisp fivers as an alternative heat source.

Avoid if you can.