I think you vastly overestimate the 318 and underestimate the Mondeo. I was keen not to bring Mondeos into this thread as the point of the thread tends to get lost as 10-15 'OMG LOL MUNDANO' people descend into the thread, but they are far from dull to drive. I find driving the Mondeo great fun, if it bored me solid it'd have gone long ago. But this, I feel, is beside the point of the thread.
Your 318 didn't feel like 11 seconds, but then we always remember our cars favourably, don't we? My Xantia didn't feel as slow as 11.6 seconds to 60 but I've no reason to doubt the performance figures.
The 318 is 115bhp - it has a decent enough chassis, shared with the far more competent 328i, but it doesn't have the power to really exploit this. I know R124 will claim otherwise, but then he also claims his 728 is fast
As for reliability, BMW's, especially older ones, are not what could be accurately reffered to as 'exceptionally reliable cars'. You'll get people who've never had a days trouble but on the whole, stuff does break, and stuff often costs money to fix. This is why I'm having to ensure I have a surplus of cash after I buy one myself, so I can fix it when, not if, something breaks.
This is fine if the money is there to sort it, but if the money is there there is simply no need to be driving around in an H reg 318.