"If I provide some service - say product support, for example - through "myfantasticservices.co.uk", and my customers get into the habit of just typing "myfantasticservices.uk", then when the registration on the latter expires, I'm going to have a lot of pissed off customers. I might extend it just to avoid that.
That's why this is an underhanded move. It's an attempt to lock people in."
While I agree, its also quite a cynical view to take, they have emailed with plenty of notice so that you can tell them NOT to do it.
To be fair the other registrar that I use actually phoned me and asked if I wanted them and I said yes (Ill note that they are actually £3 a year cheaper than 123 for uk domains too!)
Given the scenario you mention if they hadnt given the option you'd be a bit pissed off if you didn't buy it and someone set up a site advertising handy-Js on myfantasticservices.uk