Somebody said on another thread that it was to be used by BA,EZY & MON airlines for ths summer, but how true that is its anybodys guess.
Looks like the aircrafts configuration would be suited to all three airlines. Below is some information taken from the Titan website
For ultimate comfort, our Titan Airways A320 will be configured with just 168 brand new all-leather seats. Limiting the aircraft capacity to a maximum of 168 passengers allows for a roomy minimum 31 inch seat pitch throughout the cabin. The seating will be versatile too with approximately 5 rows of variable geometry seats (subject to change) making it possible to offer many variations of split standard/club class cabin. These ingeniously designed seats will convert at the touch of a button from 6 abreast to 4 abreast with a drop down central table.
Sounds like a good fit for BA. S12 saw Titan operate a large number of BA flights using a 737 or 757 aircraft.
It wouldn't be the first time BA have leased a aircraft to act as a standby at LGW. I remember back in 2011 they leased a A320 (G-STRP) from Astraeus for much of the summer