Buy monthly sovereign or save up and buy a 1 oz every few months

I’m unsure what the better way to go about regular investment would be.
Putting aside a set amount each month and after 3-4 months ish in my case buying a brittania or just taking advantage of the dip and getting a sovereign every month which I could afford to do.
I just don’t want to save up and watch the price climb back up in that time but am aware there is less premium on a Brittania.
Any thoughts would be much appreciated.