Be wary about spending money on FI ratings at the moment.
There are very few jobs around and even those are not well paid. The larger schools (Bae etc) are looking as WWW stated, however you need 1000 hours instruction given and a MEI/IRI. As a new FI (restricted) you havn't a hope. Also Oxford have laid off some 20-25 instructors this year already.
I would try and get into banner towing or simalar. Or you could do what i did and buy a share in a PFA airplane and hour build at 6 quid an hour (800 quid for a share and you get that back when you sell it). that 5 grand will get you over 800 hours.
Sorry to be negative but thats the market at the moment.
BB