Instead of going BMW OEM gaiters, invest a few dollars in Rancho RS1952 shock boots.  These will cost in the neighbourhood of $20 for the pair and they fit the K forks perfectly.  I'm personally a fan of gaiters over deflectors.

EDIT: Sorry, I thought you were referring to the gaiters to protect the chromed part of the fork tube.  Need to read closer; I have a myopic view on gaiters, I guess.  As for the rubber boots to seal off the fairing, what Rick said below.

In your neck of the woods I would go for the gaiters that attach to the fairing and go round the forks as well as the ones Rob says that protect the top part of the fork that is usually exposed.
It would be a rare day that the tank getting hot will concern you in Newcastle and preventing the cold air comming up to meet you would be a priority for me.

RicK G wrote:In your neck of the woods I would go for the gaiters that attach to the fairing and go round the forks as well as the ones Rob says that protect the top part of the fork that is usually exposed.
It would be a rare day that the tank getting hot will concern you in Newcastle and preventing the cold air comming up to meet you would be a prioirity for me.

You a right RicK G. Protection from the cold in Newcastle gets priority over everything else. Gaiters it is then.
Thanks to those who responded.

best regards

geordie boy

Think Motorworks do a pair of gaiters for about £18. Fit and forget plus your fork tubes and seals will last longer than you will.
Would recommend making a few small holes near the top, in under the fairing. Otherwise the air can't escape when the forks compress. Ever seen baggy looking gaiters on an old bike?
If you are concerned about getting a bit of air in, you can replace the fairing rubber thingeys with a rubber lip that goes around the fairing hole and has an air scoop on the bottom edge to draw air into the fairing.

You are correct. The original fork boots were removed and replaced by scoops to help with under tank cooling.

I had to remove the scoops when I went with fork-mounted road lights, and didn't really notice any difference in tank cooling.

This winter I'm going to take steps to add insulation to hopefully rectify the tank cooling situation (and post my results). It appears the k-bike was originally designed and tested naked, with fairings only added later on. Unlike today, designer's didn't consider much in the way of insulation to improve performance &etc. So, theoretically, by adding insulation to the old bikes one can improve horsepower and performance as well as solve the problems of overheating fuel tank.