I have an active Limited Company that has technically ceased trading in the field it was in.
Rather than close it, I wondered if there is any advantage to using it for my day, swing or short term trading? I could easily change the SIC code with Companies House.
Clearly tax incentives will be the main plus if there are any.
Any pointers would be greatly appreciated.
DC7 
You currently can’t use a company account on Trading 212, so you would have to do it on a different platform. But it could be useful, just depends on your investing style
DC7 this has ups and downs and it is not an automagic tax saving and differs massively between trading habits.
Most important thing to know is investments of company profits are not eligible for corporate tax relief nor you can expense them. They’ll stay as assets on company books until a time they are sold. The best way to figure if it’ll provide any tax benefits is I guess go to an accountant give them your last years personal trades and ask them to calculate if it’d done any savings.
I, myself arrange my transactions so they are always filed under capital gains (holding for 12 consecutive months at least) this way I can arrange my gains and losses to be under 12K annual allowance and pay no tax. (companies have no tax free allowances)
But your circumstances will vary, since you said you do swing and short term trading. I do option trades for short term and have no other way to file these but income tax and it hurts 
I don’t think many people in T212 community will have experience with trading with a company tho, let us know if you find any useful information.