It might be standard practice but that doesn't make it correct. The FMP will normally authorise such requests but are supposed to report them to the CAA who will follow up any possible abuse. Perhaps you should talk to UK FMP and alert them to a possible misinterpretation of the rules.
"Routine positioning flights e.g. returning empty after an evacuation or positioning for fuel, or positioning to an airport to collect a patient some time after arrival (i.e. not time-critical) do not qualify for the use of STS/ATFMEXEMPTAPPROVED."