What is the best way to fix this, Can I use a spirit of some kind to take back the second coat of wax and then re-apply?
Also. i have noticed that the wax, even after a few weeks still keeps a slight waxy feel, does beeswax not harden? what other potions are their in terms of wax?
You do not state your location, are you from Merseyside?
I would expect methylated spirits would clean up some of the present wax, but some will likely remain in the pores of the wood.
A belt sander and the word "smooth" are rarely used together. The belt sander will do a good job of removing the dirty/oxidized surface, but the grits are normally rough.
What was the grit on the belt?
A rough surface will be more of a challenge to clean off the present wax, and if you attempt to sand with wax on the surface, the wax will melt and mess up the belt.
There are many options for wax. Sorry, but I am familiar with US sites, so this is Woodcraft.
A stand-by in the US is Johnsons Paste Wax. I purchased a tin decades ago, and it is still usable.
In the above link I have used George's Clubhouse Wax, which is a mix of beeswax and shellac. Very easy to apply, but you should have a very smooth finish, e.g., 200 grit or finer.