Terminal leave is 20 working days - used to be 28 days when they included weekends in the calculations. So grab back that week and a half I'm afraid.
I was always told GRT is yours to use as you please (except work) so you don't necessarily have to engage in approved activities. According to the JSP, it comes under the heading of Individual Resettlement Preparation (IRP), which "should be interpreted in the broadest sense for resettlement purposes and may include periods spent applying for jobs, attending interviews, employment and recruitment fairs and preparing CVs. IRP may also be used for activities related to house purchase and relocating children in schools."
And that's exactly how I will use mine when the time comes.