She says that he is going to Dunkeswell and Old Sarum and then over the IoW.
Well, I wouldn't risk that route as being sufficient for a qualifying cross-country.
However, Bournemouth to the Hengistbury Head VRP, then transit to the Sandbanks VRP to set course to Dunkeswell is 63 nm. Then fly from Dunkeswell to Old Sarum via the Wells Mast VRP (to avoid the very busy military area surrounding Yeovilton and Merryfield) and that's another 64 nm. Finally, Old Sarum to the Stoney Cross VRP and thence to Bournemouth is a further 23 nm, giving a total of exactly 150nm. I would consider that a sensible route, with an eminently sound reason for the Wells Mast VRP dog-leg.