Hi Jis
It sounds like you have very good control. I think it is very unlikely that one pint of beer would have an impact 9 hours later. Beer is quite high in carbs (about 25g per pint I think), higher than lager, but only marginally.
I have done some intensive testing of alcohol's affects on my blood sugar, and it is very marginal.
I have been testing for a year, and you do get the occasional strange reading, high or low, but I would not be too concerned about one reading, especially in the 8's.
Diabetes is a pain, but you also have to live. If you enjoy the odd pint, have one!