Isn't the thread size different between the Mk2 Ph1 and the Mk2 Ph2? Cos the Ph1 is front mounted, and the Ph2 is rear mounted, I tried a Honda CTR aerial on my Ph1 and the thread diameter was too small IIRC.
I had previously used the the CTR aerial on my Mk4 POLO, and now my mate has it on His Almera GTi, so those threads are obviously all the same size.
If the Modus thread is large enough for the ph1, and radio reception is good, I might have ton try one of those. Aren't the Renault 'beesting' aerials amplified like the Honda and VW 'stings? IIRC the 'sting masts with the extra worm around the outside are amplified.