The reasons for UK CAA's differences to the ICAO standard for runway aiming point markings is given in the UK AIP GEN Section, 1.7-35:
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a. The shape of the marking means that 1/3rd of it is outside the centre 3rd of the runway and is therefore less prone to rubber contamination.
b. The marking is more easily identifiable as it differs from the TDZ markings.
c. It provides enhanced visual cues for the angle of approach.
EASA requires the same as ICAO so not sure if UK CAA will stick with the difference. Although some already have, I don't think UK airports need to suddenly change markings to comply with EASA/ICAO, particularly if there are no safety implications in retaining the UK markings.