Not actually fighting with you easyrider, I was more pointing out to rodenal that I don't think the rust problem with BMWs is as bad as is being made out.
Clearly yours has a rust problem (although I don't think being by the sea is the sole cause, it must have been started by chipped paint left unattended).
If I were in your shoes, I'd get some quotes for the rust repair work, some trade-in values, and work out if it makes sense to get the repairs done. You've been looking at replacement cars for well over a year given your previous threads (whether seriously or not I've no idea, but clearly it's been playing on your mind for a while), so I doubt even repairing it is going to offer the change your heart desires. The end result is likely going to have to be a replacement car, regardless of whether your E46 can be repaired cheaply or not.
So yeah, to re-cap, I'd get some repair quotes, and some trade-in values (for both current state and fully cosmetically repaired), work out from there if it's worth repairing, then make a decision on what to go for next. Either way though I'd not be spending £15k on an E90.
Thanks for the input
