The theoretical knowledge exams for an Airline Transport Pilot Licence are the most comprehensive and therefore if you have passed these already, they will be valid when applying for a LAPL, PPL or CPL.
ATPL (A) exams are also valid for the IR (A). However, the ATPL (H) exams do not include all the relevant material for instrument flying and you must take additional exams to obtain an IR (H). All exam cross-credits are applicable as long as your passes are valid, as set out in the Validity of exam passes section above. You do not need to have obtained a licence in order for exam cross-crediting to apply.