I have looked at day shelters and one question kept popping up in my mind was...what happens when the wind changes direction like it does so very often.
Are they easy as a brolly to re position ( pegs and all) and if no action was taken quick enough would they act like a sail and disappear over the horizon?
I worried about this John, I have an Aqua Fast & Light which was a barely used second hand bargain around the price that the op is talking of spending.
Anyway, to cut a long story short it's very stable with the long storm poles fitted to the front (in addition to the two shorter ones).
If the wind comes from behind it just pushes the force down on the storm poles, if it comes head on it pushes down on the four strong ribs which touch the ground, the ribs and the storm poles kind of work against each other in pushing the whole thing to the ground from either direction and a sideways wind doesn't really affect it at all.
Not sure about other shelters but I would think it's the same principle, I think the important thing is to have four ribs touching the ground at the rear as some shelters are just brollies with sewn on flaps and only have two ribs touching the ground.
Apart from the general quality, the other thing I like is that it can be lowered right down to within a couple of feet of the ground in case the wind changes to a head on and it's deep enough to still keep out any rain.
If a shelter doesn't come with storm pole attachments they can be bought separately for a few quid.