EASA requies instructors to have theoretical knowledge and experience requirements '....appropriate for the instruction being given'.
So it is highly likely that the PPL/FI will have several hundred hours of relevant personal experience of grass strip operation, navigating around the UK under VFR and experiencing UK weather over a few years as a PPL holder, probably one who has used an IMC Rating. Which will be of a lot more use than someone whose sole experience amounts to minimum time beacon-bashing under the hood or a handful of hours staggering around the sky in a Seneca on one engine wth an instructor in the other seat.
Own flying skills, ability to impart instruction and knowledge of the exercises to be flown, plus appropriate theoretical knowledge will be no lower than the present 'standard' - and hopefully the focus will be on the ability to impart instruction.
Additionally, it could well be a less expensive, albeit slower route to the airlines for those who yearn to fly people-tubes. Obtain PPL, IMC Rating and Night Qualification and build up flying time. Apply for FI course. Apply for job as PPL/FI. Get paid - and save pennies towards CPL/IR. Meanwhile, network with others and perhaps get noticed and accepted for full airline sponsorship - which will have to come as the pilot shortage is unlikely to be met any other way.......