ok so on wednesday decided to do the service on my copen think it had about 400 to 600 miles left before on the dot with the 3000 miles jobby and all was good oil change filter ect but like you said Adam K the oil filter was a problem big time ! it was about half a cm too wide to get through the gap and in the end i had to take the front bumper off and the air filter box and also the intercooler and the air intake pipes just to get it out... jeez but now it has a proper stubby oil filter now and before putting it all back on cleaned all the pipes and intercooler up so now its better visually then before oil i used was castrol magnetec
Although not applicable to me and never seen this actual space issue, but could you have hit filter with a hammer to collapse it that 0.5 cm. OR get small hacksaw in there.
Do they still have toffee hammers? That's taken me back to the Christmases of my youth. Breaking up the toffee with the hammer and then use it to crack your nuts on the hearth of a roaring fire. We had no iPads or mobile phones but we did have poverty, rickets, TB and of course broken teeth off the toffee. Happy days.