Has anyone kept reptiles outside during the warmer weather?

I have on order various flexariums which are going to be placed on the conservatory.
Heating is all sorted however i am undesided when it comes to the UV requirements.
These tanks will be housing various chams.

I have left chams in there during the day before climbing around on the house plants. They appear to get brighter coloured and more active.

With that in mind i cant deside if natural light will be better that the artificial tubes during the summer.