Am not sure on the Astra, I have a MK5 I should know that.lol.
Menz is an abrasive so along with the light hand cut pad it should and will do a much better job than SRP. SRP will just fill them not remover them.
Menz with the pad will try to remove them followed by BF GEP to fill them apply a good sealant or wax and you will have a nice finish.
All depends on the sort of swirls if its bad it may need to be machined out.