Again, thanks very much everyone for all your help!
IRF, i followed your path to Metalmickey's work and have played it on my Vita, and you are certainly correct, he has fixed the sprite and it runs way better than how the original JSW version was running.
I must credit Norman Sword once more though.... and certainly no disrespect to Metalmickey, but the Willy sprite in Norman's VK3 game is, for me at least, running super-smooth. The Metalmickey one does actually stammer a little bit. ...Like i say though, it's still awesome, a huge improvement, and the Metalmickey version of JSW will be the only one i play from now on, when playing 'regular' JSW.
I guess the icing on the cake is, along the way i've discovered Norman's crazy games hehheh
After playing Norman's game for 20 minutes, i went back to regular JSW and it was like it was in slow motion hehhah...Just brilliant
Norman Sword, wow i must say i've been playing your game (JSW 128 VK3) and it's amazing what you've achieved.... and yes you truly have perfectly corrected the Willy main sprite!
I've been playing your game on my PS Vita, with its OLED screen (using RetroArch & Fuse emulator), with a CRT overlay effect and it's just brilliant. ..Looks stunning & plays stunning.
The additions you've made to the JSW experience are truly mind-blowing to me, especially the way that Willy is invincible for a short time after losing a life, and also the way you can slowly break through floors.
....now the tricky bit ....Dear Mr Norman Sword, is there any chance you can be persuaded to release a standard regular version of Jet Set Willy but with the main sprite 'corrected' in the way you've achieved it in your game JSW 128 VK3?
Sorry i know it's a bit cheeky to ask, but i figured it's worth asking as it may be something relatively easy for you to do, considering your skills hehheh