I am not a Virgin driver, however I think that several high capacity operators have a policy of not circling lower than normal circuit height if it can be avoided with again most having a hard limit of 1000ft HAT. This normally requires a runway aligned approach if there is any doubt about ability to circle at normal circuit height i.e. 1500ft HAT.
In my experience operating into some of our Towered regional aiports the ATIS will report FEW 1800 suggesting that a DME Arrival will be O.K. but when you arrive the actual is SCT 1500 causing difficulty with the policy and hence a go-round ensues.
I can't answer why ATC are not aware of the policy.