you will have to work it out yourself on local pricing
in case you don't know , lpg gives approx 7KWH/litre , heating oil about 10KWH/litre
so you can do the comparison yourself , but don't forget..........
installation cost of night storage heaters is cheap and , for the moment they are still about second hand in areas where natural gas has become available ; effectively zero maintenance ; if you have thick walls they are probably the best method in my view , because the walls are a heat sink
installation of lpg/gas is expensive , and oil is pretty expensive to maintain ; annual maintenance contracts are highly recommended , and despite that my neighbour has just had to pay £800 after 10 years use for a rebuild on his oil system ; gas systems are cheaper to maintain
don't forget standing charges ...you already pay the electricity one , so probably not much on - cost there
lpg , tank rental ? tied to one supplier ...not me !! so get some installation quotes , amortise the cost over 20 years , and see where you get to !
where I live it is a no brainer ...it's electricity !! for new build there are new alu radiators , much smaller but expensive ; combined with underfloor cables now that heavy insulation under the screed is the norm
and don't forget that if you have economy 7 you can operate wash machine/dishwater / hot water etc during the night , so you have to factor that saving into the calculation
where do I live? well france which is 80% nuclear and with low electricity prices to match
don't forget to post some quotes on installation cost , also elec/lpg / oil prices [ see if you have a local buying group on lpg and oil ...if they can come round and empty a tanker they will give you a deal ! their trucks cost a fortune to run now !
despite your comments about your current electricty prices I would be surprise if economy 7 type storage heaters don't work out easily the best deal !
or , of course , you could always move somewhere where there is natural gas :)