is it 220
- shortest distance, or
- routesheet distance?
For a DIY then it depends on the answer to Mattc's question. 220km shortest distance between controls isn't a problem as you'll get the appropriate bit of time on top.
220km planned route for a ride that's 200km shortest distance between controls is ok, but not great, for a DIY. My first DIY 200 was 230km due to the route I took but it was nice weather in the summer. On a hard winter's day those extra 20km could mean the difference between 2 points and being out-of-time and getting nothing.
For calendar rides it doesn't matter as long as you advertise it's 220km and not a plain '200'. Some people would be annoyed to enter a 200km ride only to find out there's an extra 10% when they get the routesheet.
The Upper Thames is 213km by routesheet, but it's possible to shave off most of the extra 13km by taking the more direct main roads, but you'd lose out on the great choice of route/roads Phil has made.
Also, for calendar rides, I seem to remember that BRM rides can only be a maximum of 10% over-distance. You can't have a 230km BRM 200. That does mean you can have a 659km BRM 600 though. Eek!