the kebabman - I suggest that you obtain a copy of the current edition of LASORS in order to research what the privileges of various licences and ratings are. It is now a requirement that all licence 'applicants' should know what their licence entitles them to do - and how to find out the answer.
Once you've passed your ATPL(A) exams, they have a limited period of validity within which you must take the CPL(A) Skill Test - and once you've done that, you must pass your IR to keep your ATPL knowledge valid - and that also has a limited period unless you revalidate your IR. To 'unfreeze' your ATPL you will need, amongst other things, 500 hours as the flight crew member of a multi-crew aeroplane..........
At present in the UK there are quite a few FI(R)s chasing not a lot of FI jobs - there is little throughput of pilots to the airlines at present, so things are unlikely to pick up that soon. If you don't achieve 100 hours flight instruction towards a licence in the 3 years of your rating validity (of which 30 must be in the final year), you'll then need to do both a revalidation FI proficiency check (£190 plus 1-2 hours hire) and attend a revalidation seminar (2 days, £250-ish plus accommodation....). But if you do make the 100/30, then you can choose either the proficiency check or the seminar - at the moment. However, mandatory proficiency checks every other revalidation will soon become compulsory...........