New tube in kitchen light

The cheap little Osram 840 in the kitchen light went.
Shame too, i'd only just stuck an electric starter in it.
Decided to stick another tube in except this one isn't a cheap little one but a British made Osram L65/80/23 T12
Looks fantastic in it too.
The fitting isn't supposed to take T12's but it does without complaint with the exception of the diffuser supports being a bit squeezed.
Has a 65W ballast in so why not?

How much brighter are these type of tubes with a proper 80w ballast?
Never seen one running with an 80w one.