The aeroplane is not listed on the BGA website as an approved type so, I presume, will need approval by them before being used. You don't say where the aircraft is registered Ireland/elsewhere and as what. Is it an EASA powered sailplane or a Irish CAA SLMG?
It has never been a requirement to have an AOC to rent out an aeroplane. flying clubs have survived by renting aircraft form individual owners. An AOC is required for commercial air transport, freight or passengers. EU 965/2012 deals with commercial air transport operations so not applicable here. Whilst we are members of EASA there is no need to change the country of registration but I presume the BGA will need to approve the type for use by gliding clubs in the UK.