Hello Joshua,
I think you will find that there won’t be any cure for this, with your current engine.
The warranty company may dictate an ‘official assessment’ of the oil consumption via a main dealer - and this will cost. Make sure you don’t end up with the tab! This requirement will of course erode into your warranty period, and you end up in running out of time.
I’m not sure if the seller’s responsibility is for 30 days only, or if it is the 3 months you talk about, so you will need to take legal advice on this - CAB should help.
It’s essential that all your dealing - past and going forward - are recorded in writing ( e-Mail should do) with the seller.
In my opinion, you should seriously consider rejecting the vehicle and getting your money back, since I would not see a way forward where a quick and convenient resolution would be practical.
Perhaps you could let us know how you get on Joshua.
Kind regards,
Gareth.