Scissor jacks aren't the best. One thing they have got going for them though is they are nice and compact and as you say it 'did the job' so better than having nothing! :)
I have two jacks in the car! - Scissor jack to get the car up about 2mm and a bottle jack which takes over and makes life a darned sight easier :D
I have a pair of bottle jacks in my car, means I don't have to remove the jack point covers for the useless scissor jack, and they're also a lot better seeing they lift Land Rovers :P
I was gutted, I bought mine from screwfix - £13 :) only to find that they are about 2mm too tall to just go straight under the sill, which is why I need to jack it a tiny bit lol
James, you got a link for your jack? mines not lowered and on 19's so i shouldnt have this issue?
Sal, I believe its this one: http://www.screwfix.com/p/2-tonne-bottle-jack/54957
as I say, its not short enough to just put straight under, but for 30 seconds scissor jacking up a few mil, and then bottle jack under and let the bottle jack get on with the rest, it works a treat!
The only issue is that when your jacking down, you need to put the scissor back into the groove, and lower it so the scissor jack takes the weight, then compress the bottle jack the rest of the way, remove and then drop the last mil's with the scissors :)