New Judge, the sale of 99.5% Ethanol is subject to extreme government regulations in the UK and the OP would not be able to purchase it. Companies such as the one offering the product will legally need to establish the use the product will be put to.
Currently, only bona fide research establishments in the scientific field or medical manufacturing establishments are permitted to purchase high concentration ethanol. There are complex forms that need to be completed to satisfy the necessary regulations and the forms are checked with extraordinary diligence before the sale is authorised.
These regulations have been in place since I was in Junior school, which is more years ago than I care to remember. My university laboratories last year used 6000 litres of absolute ethanol and annually, I and my colleagues have to complete government documents on its use, storage and security.
The government research facilities I mooch around in are also subject to the same stringency and they use even more annually
For those interested, the principal reason for these regulations is that in the eyes of government, duty should be paid on alcohol sales. The 500ml bottle of 99.5% ethanol at around £60 when diluted to vodka strength would be a nice little earner for someone and would deprive the exchequer of considerable duty. That is why the purchase would not succeed apart from the toxicity of the product.
Denaturing the product would permit the sale but there is no indication that it has been denatured on the website.