Not sure about 30bhp. Standard willy lump is 150. 13bhp up on the valver lump!
As for tuning the 1.8 lump, iv done it, and i am happy, but it would have been a bit cheaper and easier to go for the straight swap with the willy lump.
Mine is about as fast as a standard willy, maybe a little bit quicker,(and iv drove a willy) especially as the 1.8 revs it knackers off quite happily, and has loads more torque than the standard 1.8, can drive around happily under 3k all day in it. But, if u went for the williams lump u have the opportunity to tune it further.
I need to get mine properly rolling roaded, the first time i had it done, it was only just run in, and ran 147@fly. Not loads of power, but the 2 other valvers with exhausts, decat etc were both running 127@fly on the same day, and the cups, 172s were around 160@fly
Only mods since then are k-tec manifold, BMC Filter, and rid of the cip i had (as it was poo), and it ran 169.1bhp. Bit high me thinks, but still a good comparison as there were a few other clios, and 19s there as well!