Venturi through the exhaust would be best but is costly and will need some custom fab as there is no off the shelf kit in the UK (that i know of).
If you can't have them drawn out, then leaving them to escape with as little restriction as possible is the next best thing. I still believe that 2 x 25mm pipes venting naturally is better than 1 19mm (or less) I.D. opening being drawn out through the TIP (PCV delete with catch can). Most aftermarket PCV deletes have such a small recess for the passing of the crank and cam gases that no amount of syphoning will help