If the European Patent Office has issued patents which contravene the rules, can I ignore them?

Only if you are very rich. Be clear - all issued patents are perfectly legal patents, unless some legal activity shoots them down. There is no such concept as an illegal patent. You might be able to find sufficient prior art, or other material, to invoke a re-evaluation of the patent, on grounds of information not originally available to the patent examiner who approved the patent. That can often be hard to achieve, though, and you will probably end up in court. If you wish to question the wisdom of the original patent examiner, you will almost certainly need to do that through the courts. This will cost an enormous sum of money, for even a simple case. The outcome of any patent case is uncertain, and you will very likely end up with the bill for your own lawyers, whatever the outcome.