Just out of interest, why do you want both? Apart from being outrageously expensive, if you get a job with a high hour fixed wing operator they generally won't allow helo flying 'on the side' due to max flying hour restrictions. Many helo operators won't take a fixed wing qualified pilot for fear of them jumping ship the second the market takes an up-turn.
If you are thinking of throwing your job net wide then I would suggest concentrating on one or the other!
If it's helo flying for fun (and it is fun!) then do it when your fully 'fixed' qualified.
Trust me, I have both and had to let the ATPL(H) lapse!