If the OP holds or has held an IR issued by a third country in accordance with ICAO Annex 1 within the last 7 years, there is no requirement to re-take the theoretical knowledge examinations.
ORS4 No.1090 B 5) Derogation from FCL.625(c) and (d) with respect to renewal of an Instrument Rating
Pursuant to Article 1 of Commission Decision 2014/69/EU, the United Kingdom allows the holders of licences issued in accordance with Part-FCL to renew their IR privileges without passing again the theoretical knowledge examinations for the IR, if they have held a valid IR on the licence of any third country within the seven years preceding IR renewal, provided that the third country licence is compliant with Annex I to the International Convention for Civil Aviation (ICAO Annex I)