Im buying the transformer from RS, the highest v/a I could find suitable was 200v/a.A 28V transformer must be 200VA for a 5ADC output from the project.
A 30V transformer should be 212VA but a 200VA one will not get too hot.
I went for a 5A limit in the hope that I would not need that much, so it would not keep the power supply runnin at max, and so it was there incase I ever needed such a large current.
But if you think it might get a bit warm, then I have some big industrial 24V fans I got from a old work place I will use for the enclosure. Will have them variable speed, either manual or temperature controlled, I have seen a few threads on here about making the circuit somewhere