" My base come with what looks like tent pegs to secure the base to the ground, so I'm going to use them. Plus with the weight of the greenhouse (although mine is glass) I can't see it moving around much."

hmmm. With an 90 mph winter gale, that may be optimistic.

I put our greenhouse on a steel base and put all the retaining pegs into concrete mix for posts. Has not move din 25 years.

A really strong gale can move anything not securely fastened by the constant one/off pressure of wind gusts loosening all but the most secure foundations.