Titan purchased a former British Airways Boeing 734-436 G-POWS and it's based and currently in service at LGW for summer 2018 operating on behalf of British Airways along with two Titan A320.
There may well be an additional Titan aircraft operating for British Airways ex LGW for summer 2018 but I actually think it's just the three.
I think Titan are keeping the all business layout on their A318 at least for this year anyway.