There has been a 20MPH limit in all towns and villages in the Scottish Borders for a few years now. And when introduced it was just stupid. No one liked it and it was a disaster.
Typically the speed limits change from National Limit (60MPH for cars) down to 40 or 50 limits and then to 30 within the town/village. What the Council did was get rid of all the intermediate speeds and change to 20MPH right after the original 60 stopped and this was just rediculous. Had 20MPH limits in what was essentially open countryside with no houses or even pavements.
They eventually realised they had screwed up and "after consideration" they said that changing the limits from 20MPH to 30MPH outside the actual towns and village centres would be safer - not sure how they managed to not realise people staring at their speedos on an open road to keep below 20MPH was less safe then watching the actual road?
Now the 20MPH limits are ok as they are in in the built-up (or what classifies as 'built up' in the Borders anyway) areas, where you would be unlikely to be going much faster anyway and the approaches to the towns are an interim speed between National and centre speeds, which work well enough I think. (in the villages such as mine it is a switch between National/60 and 20MPH).
There is one daft bit of road just outside Newtown St. Boswells (or it could be just St Boswells?) heading towards Melrose where it is hard to know what speed you are allowed to do as by the time you have seen the sign and checked your speedo, the limit has changed again, then add in Dual Carriageway that isn't, Single Carriageway that is and it all gets very confusing. In no particular order the speed limit changes between 20, 30, 40, 50, 60 and 70 in the space of under 1.5 miles.