MEK/Acetone won't work. Xylene, maybe, never tried it.
Methylene Chloride will do the job. It's the only solvent that has separated UV cure cement for me.
After a week in MEK it took less than two days in the Methylene chloride. It's the main component in some paint strippers. I use is Parks Pro Stripper. 32 oz is a common size from the hardware store. Brand won't make a difference but it HAS to have the MC as the Primary component.
If you want, send it to me & I'll separate it for you. 32oz is about two lifetime supplies.
RE: recentering. I use two pieces of 3/4" aluminum angle. Set the glass in place and one angle on each side. Hold 'em together with a rubber band or two.
It's gonna look like this <O>. I use a UV cure cement and wipe the edges with a paper towel dampened with Acetone. The edges are painted with a glossy black enamel. As long as it's OK for glass, it works on the lens group.