I was the same about the tax paid the £400+ tax on my 59 MPS and also the 335i and was worth it to run the cars. Although its quiet refreshing now to only have to pay £270.
Also worth remembering to get the full power from the DISI engine you need to run Super Unleaded. The 330i runs just fine on standard fuel.
I'm with dopper99 - Get an e46 M3 if you can stretch that far... amazing value cars . + The tax is only £270 IIRC