Hi Mick and Welcome! Firstly I don't keep beardies atm but here are a few responses to your post. The floor area recommended for adult beardies is 8 sq. feet so the tank is a little small for a permanent home. Also at 20" high you would have to find a way to drop the uv tube lower - the beardie needs to be within 12" of the tube max. Also you will find that glass tanks do not hold the temperatures as well as a wooden viv. The other slight issue might be that beardies particularly do not like being approached from above as this is very threatening to them.
Secondly sand. You will find no end of debates on here about substrates. The general concensus is that if you are going to feed your beardie in the viv then sand is a definate no-no for babies - use tiles, slate, lino or paper. Sand, especially reptile or calci-sand, can cause impaction which can be fatal - it is coarse and clumps in the stomach. For adults then many ppl still find a non-particulate substrate easier to keep clean. If you do wish to use sand then the best is childrens play sand which you can get from Argos or Tesco for example. It is finer, clean, non-clumping and cheap. Just bake it in the oven before use if it is too damp.
After all that I hope you enjoy your beardie - it will give you hours of pleasure.