Hi irishthump,
I managed it thanks to your advice. I still found it quite difficult to free those tabs, was using a small screwdriver and they needed a lot of effort. I changed a 181 back to dc and converted a 141 to dcc. Also had to remove the handrails off the 141 and a tricky to get back on if you don't have a small tweezers. I don't have the skills for this stuff and wouldn't dare do a speaker/sound conversion of a 141/181. Compared to chipping a 201, they are awkward and fidgety.