ROR is Residual Oil Cleaner, I get it at B&H, do a google and you should be able to find it in the UK.
Here's a link showing a teardown of a lens
Pentax 50mm f/1.4 strip-down instructions
I used this as a guide only to give me an idea how the lenses are put together. I
got my spanner wrench at Thomas Distributors (?). I only go as far as front or rear elements, any further and you can run into problems with lens alignment. I found this out on an old vivitar zoom which I had to redo because I reassembled it wrong.
On a difficulty level I'd rate front and rear elements as easy, any further and you need a good memory or photos :-)
Also a set of jewelers screw drivers is a must, small cheap screw drives can shear off tips if the screws are tight or corroded. Another tip, the spanner wrench will slip, use it Slowly or you can scratch the element.
I'm not an expert by any means, I just found that cleaning lenses and small rangefinder cameras a fun hobby and not as difficult as folks make it out to be :-)