From JAR-FCL 1.245:
(1) All single-engine piston aeroplane class ratings (land) and all touring motor glider’s ratings – Revalidation.
For revalidation of single-pilot single-engine piston aeroplane (land) class ratings and/or touring motor glider class ratings the applicant shall:
(i) within the three months preceding the expiry date of the rating, pass a proficiency check in accordance with Appendix 1 and 3 to JAR-FCL 1.240 or Appendix 1 and 2 to JAR-FCL 1.210 with an authorised examiner [in the relevant class]; or
(ii) within the 12 months preceding the expiry of the rating complete 12 hours flight time in the [relevant] class including:
(A) 6 hours of pilot-in- command time;
(B) 12 take-offs and 12 landings; and
(C) a training flight of at least one hour’s duration with a FI(A) or CRI(A). This flight may be replaced by any other proficiency check or skill test.
So it is abundantly clear that this shall consist of a single flight. The logging of a series of flights with less than 30 min between them, all of which depart and arrive at the same location as a single flight refers to entries in log books only and does not constitute the acceptance of such a series of flights for the purposes of re-validation. In any case, if you fly from A to B (30 min), have a cuppa and then take-off again within 30 min from B to fly back to A, that may not be logged as a single flight. Whereas take-off, fly a 20 min trip, land, change pax and repeat (<30 min between) would.
How would the CAA know? Because the FE who signs the 1119 needs to see the pilots logbook and checks that the FI has recorded a 'satisfactory' completion of the training flight. That will include a check of the block times; any doubt and the 1119 won't be signed.
I suggest that you make very sure that any flights you conduct for the purposes of the '1 hour training flight' are indeed of at least 1 hour's duration. Otherwise your pilots will not have completed their re-validation requirements in accordance with JAR-FCL 1.245 and would thus be flying with invalid licences. If they subsequently had an accident which wrote off the aeroplane, the insurance company might not pay up as the pilot did not have a valid aeroplane licence. So guess who will have to fork out for the damage.......