Thank you so much for all the helpful advice, it is very much appreciated.
After your explanation of the various substrates I think I am going to go with soil substrate with artificial plants for now.
I was looking at one called E-Coco which says it is coco peat and coconut husk which is actually advertised for whites tree frogs but I like to just check.Would this one be suitable. If not which ones are the best?
As far as the life span and having to look after them for a long time that is absolutely fine by me. I am a very keen Fancy goldfish keeper and they are a lot of hard work as I have 4 big tanks which I have to do large water changes on a weekly basis with a syphon tube and buckets because I can't have a water changing system but I love my fish so I do it religiously. I wont take a pet on on a whim so fully understand they are for a long time.
The crickets wont be a problem. I have a local Aquatic/pet store near to me and they always have loads of live feeder insects.
I will now go straight for the 45x45x60 vivarium. To be honest it is better for me as I didn't really want to have the expense of having to upgrade.
Anyway, thanks again for all your help and advice.