7.5 hours? Whence does that come?
From CAP 804:
3.5.2 Renewal
Where the IMC rating or IR (Restricted) has expired by not more than 5 years, the revalidation requirements of 3.5.1 apply for renewal.
Where the IMC rating or IR (Restricted) has expired by more than 5 years, the candidate shall carry out dual instruction, at the discretion of the FI or IRI as appropriate covering the IMC rating course, and pass the Initial IMC Rating Test with an IMC rating examiner in a suitably equipped aircraft. If the rating has expired by more than 10 years, then the IMC Theoretical Knowledge Examination must be passed.
This does NOT mean that you need to complete the entire course, merely that the refresher training covers appropriate parts of the IMCR course in order to prepare you for the test.
Usual confusing stuff from the Belgranists though; how else could you take the test other than 'in a suitably equipped aircraft'? In a boat??