Running rough and EPC light came on

I have a beautiful MKVI Golf 1.4 TSI (122PS) SE. It has always been my trusty steed and we have owned it for almost five years now with no major problems. A few weeks ago during a road trip, the EPC light came on and the engine started running rough. I had to limp home at around forty to fifty mph on the M4 as accelerating or gradients induced vibrations.

I could tell from my limited knowledge that it was most likely an issue with one cylinder not firing properly. When I got my destination the engine cut itself out (it did not like being in low revs) whilst parked. I restarted and it fired up with no issues. I restarted a few times and nothing, no EPC light. Everything seem to be running well. I thought this was a little odd, but let it be. A few days later the EPC light comes on again this time with an engine management light too whilst in stop start traffic. Again getting to my destination and restarting caused the problem to disappear. I was away from home on business and my dad (who knows his way around cars a lot better than me) told me to see if I could get it home the end of the following week. I had no problems after that, no warning lights, no rough running for almost two weeks. Fast forward to last weekend, I managed to get it two hundred miles from London to Manchester with no issues.

My dad hooked up his VAG device to get the read outs and we got the following (can provide codes if necessary):
- Misfire detected in cylinder four.

As well as this we hooked up the VAG to run some parameters. The idle revs were jumping between 640 rpm and 680 rpm. Misfires on cylinder four were being detected at idle, but increasing power caused the misfire to disappear as the misfire count did not go up. Returning to idle revs again the misfire count would start to increase.

We changed the spark plug and coil pack on that cylinder and did not see any improvement. We thought it might be the fuel injector so my Dad took it into an authorized VW garage (but not VW themselves) who charged £60 to take a look. They told us that there was a low compression detected on cylinder four which was causing the misfire. They recommended the cylinder head would have to come off to see if there are damaged valves or to see what else could be broken. The price for just this investigation would be £550 and the repairs to either the head or piston rings were well into the thousands.

At this point it does not seem economically viable to put thousands into a nine year old car which is only worth around £5500 (according to similar spec, age and mileage on Autotrader). However, we paid close to £10K for this car just over four years ago, so it seems unusual to experience a mechanical issue at a relatively young age for a well cared for and maintained car with low mileage. We have always had Golfs in our family and this was my first, so naturally I am quite attached to my car (as I am sure some of you are too!) So hoping not to have to scrap it. According to the specialist, this is not unusual for these engines, but I am not sure how much I am buying that.

Anyhow, apologies for any mechanical ignorance here - any input would be highly valued. Many thanks!