I would be staggered if this systemn was not registered for FITs. Would contact the vendor of the house via your solicitor. The FIT is for the system and should have been transferred as part of the sale of the property. As you have an MCS certificate this would suggest this to be the case. If by some outside chance the system is not registered, there may still be time as I beleive there is up to 12 months from the end of the qualification period (31st March) to do so. However, a FIT from 2015 will be worth a whole lot more. Ofgem also have a central FITs register and may be able to help.
To maxx out self consumption:
Change behaviours - put the washing machine/dishwaher on when you go out to work, not when you go to bed. Think about when and how you use electrcity, then do all you can to coencide with PV production.
If you have a hot water tank, fit a diverter to send excess to heat water via the immersion element. Be aware you only save the cost of whatever you use to heat water.
Look at battery storage. Do not go for a cheap and cheerful system. There is a lot coming in terms of utilising time-of-use tariffs, weather compensation and other cleverness to not only maximise use of PV generation but also to charge/discharge using the grid to avoid buying peak rate power.
Use a solar optimised car charger to charge your EV from your PV.