My brother's iphone 6 was dropped and it looks like the screen and the digitizer is damaged. On the Apple site, it says that the repair will cost around £86 for the screen replacement.

Would that repair include the digitizer or just the glass screen?

It's for replacement of the complete display assembly.

Since the iPhone 5 there isn't a separate digitiser anyway as the displays utilise in-cell touch sensors.

Yes, £86 for the complete display (the digitiser & screen are now one unit essentially) unless there there is other damage to the phone.

I've had my iPhone 6 screen replaced twice since I got the phone at the end of October. Both times Apple stores have charged me £79 inc vat. It took them about an hour and was cheaper than claiming on my insurance.