The ones I got from Haymiggan were massive too, but they fit just fine. They were only about 2mm thicker than my old 32M SIMMs but they are easily 15mm taller :-)
One of the heatsink clips was touching flat mounted SIMM so I just put a bit of electrical tape over it and it works a treat.
256Mb on your 1200 is pretty nice - certianly makes various PC game ports more fun ;-)
