Thanks or the positive comments everyone. Tas V I think agave are winter growers. It is worth a try planting in any soil that is already there just to see how things go. Last winter here was unusually dry but this winter is shaping up to be wet and cold. We have already had some frosts.
Mutant; the winter here is fairly mild. We get few frost in a warm year and maybe a dozen in a cold one the day temp is around 11-15 mid winter.
Navajoa; more the other way around with survival somethings I expected to die have done really well and there are plenty of species that I am getting much better growth from in the ground than I can in pots E.g A.ornatum. That said I thought I would try A Asterias in there this year and it turned to mush but a Loph I chucked in for a laugh is doing fine. The myriostigmas had a few losses in plants under 4 cm but once they are about 6+ cm they seem to do fine.
Biggest problem is hail damage. It is a good idea to have some sort of tree to protect them we have a tea tree that does this to some extent. It has fine leaves that don't get caught up too much in the spines. I also found some of the more tropical Pilosocereus are a bit slow and one of them scarred a little bit when we had a hard frost the winter before last but that has grown out now. Also slug pellets twice in spring and autumn are needed.

Wow, that really is an inspiration. I have been worried about frost and this has stopped me attempting something like this. I may just try a small plot and see how it turns out, I might even get my verandah back, lol.