i'd try this before getting the heads to a cleaning service. we recently had our used CET installed. unfortunately the printer sat in a crate in the hot texas summer for two months. when we got the printer up and running, we got word that we had clogged heads. the installer removed seven heads, soaked them in CET flush over night. the heads were still clogged. before we dumped $7600 on new heads, i suggested we try cleaning them with NMP. with the heads installed, we syringed NMP into the worst, most horribly clogged head (we did this because we knew it was a gonner and we might be able to send the remaining six to a cleaning service). well that head cleared up immediately and became the cleanest head in the whole carriage. we proceeded to do this to all the heads. now or heads are perfect. we have watched for any adverse effects from the NMP over the months but we've seen none. also, i did test the NMP with the CET uv ink for compatibility. ...no issues.
here's the deal. NMP doesn't melt ink. it's disperses it. head cleaner softens then gums up further up the resin clog. NMP is like a liquid plumber for the ink. it breaks it apart then goes to the next deeper layer.
the normal use for NMP is to clean urethane foam guns, and stripping powder coat. it's also the "green" solvent in HP latex ink. it feels like soap, has no scent (or maybe a light ammonia scent). i get mine from sprayfoamnation.com for $35 a gallon.