Reading the title I thought that's a long way and would involve some driving but I had not realised there was a greasy slab in Bar pot too (well was called that).
Here's the description to the best of my memory. At the bottom of the SM entrance pitch, facing away from the rope take the obvious hole/crawl at the end of the chamber going down a slope, go down that. After only 5m the passage enlarges but do not continue that way. Instead, immediately turn right and enter a separate chamber. At the end of the chamber is a calcited rift, with a small hole in the floor. Thankfully that hole is not the way on so instead climb up over the rift and follow the flat out bedding above. Initially make your entry on the right of the bedding but make your way to the left where it is larger. You will reach a 2m climb down after about ~25m.
To the right here, is the alternative way down, requiring another rope, accessed by a deep rift on the far-right-hand side. To get to the pitch, one would need to descend the rift and once on a floor of the rift look for a side rift basically behind you when you are descending to reach the pitch. Don't follow the rift to the end.
Anyway back on track, at the bottom of the 2m climb is a rocky crawl at floor level on the left when facing away from the climb down, follow this for a couple of meters and you will pop out an enlargement. Bar pot, is up a short climb here. The greasy slab is diagonally across from where you enter and is normally marked by a hand-line.
Sorry I have very good memory for passage layout, but not for the names, hence why I forgot what that alternative route is called, which needs an extra rope. It's a fun side adventure btw, but is definitely a harder route with an interesting squeeze on-route. (I think it may had been the original way in?)