I'd also suggest some navigation that has direct practical application to the CPL, such as Dundee-Lanark-St Abbs-Dundee; or up to Aboyne then over towards Dalwhinnie and back to Perth. It'll give you the variety of open FIR and controlled airspace use, together with decision-making skills (especially in wintertime over the highlands) that will build the confidence needed to manage a Commercial flight, and make your CPL training much more relaxing
Try not to think of it as hours-building. Think of it as experience-building. Anyone can drill 150 hours-worth of holes in the sky. Make it count (ie don't forget general handling skills too; and don't forget to use the available radio-navigation aids to assist your VFR flight - and I don't just mean GPS
)
Good luck