Stop and think for a minute:LASORS B1.2 is a little out of date. The second reference to 12 months should be 18 months
Validity - The RTF written examinations and
practical test are valid for a period of 12 months for
licence issue. Where a candidate completes the
examinations for a FRTOL in conjunction with a
course of training for a JAR-FCL private pilots
licence, the validity of the radiotelephony
examinations may be extended to 24 months from
the date of passing the last PPL theoretical
examination, provided that all examinations are
passed within a 12(18) month period and that
application for both licences is made concurrently.
PPL holders who subsequently apply for a FRTOL
will be required to meet the 12-month validity
requirements.
Now if you don't complete the RTF Practical within the 18 month window, you wil have to take the RTF written again as it must be taken within 12 months of the Practical if you are not taking advantage of the option to complete all exams within the 18 month PPL window.