Sounds like you handled the situation well. It is very similar to one I had a couple of weeks ago.
I was P1, flying with a friend from Yorkshire down to Duxford. The weather was forecast ok with some poor vis to the East but clearing to the South. We assessed that we were ok to go and off we went. Pretty quickly we saw what can only be described as a wall of cloud which looked to be thinning out to the South. We adjusted heading slightly to avoid the worst of it and descended to try to get under it. It was soon apparent that this wouldn't work as we were at 1000' with the cloud still closing in around us. I made a decision to climb while my friend plotted some bearings and tracks using a VOR and NDB (we are both IMC rated). We were receiving a RIS service and things seemed fine but my workload had gone up immensely. While we were safe and knew where we were, I wasn't totally happy with the situation. We continued for about another 15 minutes and got a wx report stating that the cloud was still down to 1000' and it certainly wasn't clearing as forecast. By now we were at 4200' in thick cloud and it started to rain. Neither of us wanted to do the whole trip in IMC due to the high workload and we were also concerned that it may deteriorate even further (maybe embedded CB) so we calculated a new heading and routed back. Within 20 minutes the cloud broke and we were able to descend and route back home in VMC.
Despite all the training it was still a little unsettling entering IMC like that. As others have said, remaining current on instruments cannot be overstated. I learned a lot that day and it will hopefully make me a better pilot.