Thinking of getting a second hand Plug for hacking around on, I have to admit one of the reasons is that they look lovely but also because they seem pretty robust and I can get one second hand for about £250 or so from gumtree. What do people think of them as a simple hacker?

mine has been used as a city bike since they first came out (how long is that, a couple of years?) and its been great.
you are right the frame is very robust (heavy but it doesnt really matter)

pros:
keep it simple stupid
paint seems good quality
stock bottom bracket and headset rolling nicely
brakes work well enough, i only run one cause i have mine fixed but it does the job
front wheel hub seems in good condition

cons:
if you run it singlespeed then the stock freewheel is pretty minging, but thats about 12 quid to change.
if you run it fixed be wary about the threads where the sprocket screws on, i managed to strip mine, it might be cause the threads were made of cheese or it might have been my hamfistedness. end result is i have a shiny new rear wheel.
stock tyres are fairly heavy, but thats easy changed.

there are no braze ons on the frame – absolutely nothing. so mudguards are gunna have to be temporary style ones or crudguards. also no attachments for panniers or waterbottles, but it either bothers you or it doesnt.

all in all a good bike. it was certainly better value when they were £400 quid and not the £550 or whatever they want for them now, which is a bit crazy.

Looks nice, did you not get on with those bull horn bars it came with?

they were alright, but i just fancied flats

Same happened to the thread on my rear too.

Locked the back up then nothing…sprocket was dangling down and the threads were (thankfully only partly) stripped.

Probably down to poor technique though, was fairly new to riding fixed at the time.

Mine was an '08 model, I believe they may have changed the hubs since then…