Is my six-year old touring bike worth repairing? My touring bike (which I use for commuting) needs repairs which will cost £200... half the price of a new one. 

I am not mechanically-minded.... and I am too busy and too old to learn!

A new bike will cost twice the price. But with the new bike, I get all the things the repairs will bring.... plus new wheels, new tires, a shiny frame (the current one is scarred but not damaged).

The bike shop say repairing is the best option. 

I'm thinking.... keep the bike over the summer.... and buy another when the end-of-season sale comes along.

The repairs are: a major service, replacement of all the drive mechanism, etc.

Advice please!
As LBS mechanic, I also would recommend to repair - the cost is sufficient. Your bike will be almost as new.
So if it's a bike that worth repair (like mikes mentioned), and your tires and derailleurs are in good condition yet, go for it.
If you know that you should replace tires or derailleurs soon, better is to buy a new one with all parts new and a warranty.  

Edit: if you will anyway buy a new bike soon, you should consider whether you want to do all this repair, or a part of it will be enough.