There is a white one running around Cobourg, saw it for the first time yesterday
The wife parked beside it, she has a 2000 323CIC, the over all length was about the same, 1 series appeared to be a touch narrower, but with top up the over all height was higher
Surprised to read there is no power seat on the 135
Did you have a wind screen for the time you had the car?
There nothing like cruising the back roads with the top down 
Power seats are optional in the 135i. They are a part of the $3k(!) Comfort Package. I've got the MSport package in my 135i and I certainly don't miss power seats. Then again, I'm the only one driving it, otherwise, memory seats would be nice...but definitely not worth the coin in my eyes.
I'm not a huge fan of the look of the cabrio (or any cabrio for that matter). If I wanted a drop-top I'd get a roadster -- no they don't look like an afterthough, chop-top.
If I were in the market for a BMW cabrio I'd go with the 328i for the money. If you're looking at cabrios...your probably not as interested in the performance. For the money, the 328i is better looking, has more room, a hard top and plenty of get-up-and-go. If performance is the name of your game...stick with the coupe (and keep the options to a minimum) for a great peformance buy (no bias

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Regarding the age of 1 series shoppers, 1addicts did a poll -- 49% were between ages 25 and 35, 12% between 45 and 60 years. Not exactly a lot of grannies...