Which Stronglight crankset? Early ones like the Mod93 if original to the bike are ISO, recent models are often JIS.

If you replace ISO with a JIS, you have a couple of issues in measurement. Your spindle is offset +2mm to the drive side. The VO is not. But JIS gives you a wider chainline. So, take (118.5mm +2mm) less 6mm (ISO-JIS diff) = 114.5mm. I'd go with the 116mm.

I'm actually running a Mod104 on a 118mm JIS Shimano (English thread frame), and my chainline is just a little wide, but not much.

Look for Sheldon Brown's fixed cup removal tool. I've used it. Maybe $6? worth of bolt, nut and washers from the hardware store. Works like a charm.