Don W wrote:

Alcohol is so heavily taxed in the UK and this is particularly cheap.

No - spirits are subject to excise duty. Isopropyl alcohol isn't a
spirit...

Does anyone know how much UK tax should be paid on 230 ml of isopropyl
alcohol?

Customs and Excise probably do... You could visit their web site.
This link may help - http://tinyurl.com/k8ur4