HMRC tried to fine me a couple of years ago for not submitting a tax return. I had informed them I'd been out of the country for 5 years but apparently they didn't have this on their system. The only way I could sort it out was by calling them. I used Skype to try and call them on their main number but like you [MENTION=314]Arthur[/MENTION] I got a series of robots and put in a queue which eventually hung up on me. Then I found a number for international callers and got through pretty quickly. The guy sorted everything out for me and cancelled the fine. It's worth digging around to see if you can find another number to call.
It's also worth noting, HMRC like to send out penalty notices even if it's their own f*** up. I was a contractor before I left the UK and my accountant submitted my tax return. The last time it was submitted they sent me a penalty notice with a cancelled fine (a final warning) that I had failed to declare I was repaying my student loan. This was despite the box clearly being checked on the forms and when I checked the online system, plus the fact I'd actually paid the student loan money I owed to HMRC. I called them up and they said someone had unchecked the box but couldn't tell me who it was or clarify if it was actually them. They just blamed me and said I'm lucky I didn't have to pay a fine. I'm still pissed off about it
It's also worth noting, HMRC like to send out penalty notices even if it's their own f*** up. I was a contractor before I left the UK and my accountant submitted my tax return. The last time it was submitted they sent me a penalty notice with a cancelled fine (a final warning) that I had failed to declare I was repaying my student loan. This was despite the box clearly being checked on the forms and when I checked the online system, plus the fact I'd actually paid the student loan money I owed to HMRC. I called them up and they said someone had unchecked the box but couldn't tell me who it was or clarify if it was actually them. They just blamed me and said I'm lucky I didn't have to pay a fine. I'm still pissed off about it