Looks as though your gap years are behind you…You’re probably now paying taxes, building a credit history and not living with your parents anymore. If you have been tapped as you say, then someone thinks you have something to offer the next generation of designers who are still in school (or it is just passing happy talk).
There is nothing wrong with teaching if you take the right perspective. Making as many contacts as possible in your first 10 years out of school should be one of your high priorities. After those 10 years you’ll have something of a network to fall back on and use to advance your career. I don’t know how flattery and honor work in the UK, but if you let that kind of sentiment go to your head you might end up teaching for the remainder of your career. If you get the teaching gig, give the students value in return for their tuition. Just as you would as a designer working for a client who is paying you a fee.
If the school you’ll teach at as has kept up with technology, then you do not have to worry about falling behind. Working only 3 days a week will give you ample time to raise your skills in an environment that has less stress and no deadlines and will make you more attractive when you go out formally to get your next industry job. ( I advocate that you are always formally out there looking for your next position however)
The only thing I would warn you about teaching is that it can dull your edge. Be weary of this and keep pushing yourself to take on more projects, sharpening your skills and networking with other pros. There are far less designers who have a heart attack that are teaching than those working to meet client deadlines, flying to the far east or fending off IP lawsuits.
Good luck…