Chausson 610 - Exhaust Filter at Limit

Hi.  Apologies if this has been covered before - I did search the forum but couldn't see the topic.   So, we bought a Chausson Welcome 610 (16 plate with around 21,000 miles) back in July.   Done about 1200 miles on it so far and loving it.  Today we took it out to a local site (15 miles from home) to give it a bit of run.  On the way home today, engine seem very sluggish, no top end power, continually having to use low gear.  After a few miles driving the emissions light on dash came on, followed a bit further by 'Exhaust Filter at Limit, Drive to Clean'.

Being a bit of a newbie to motorhomes (but not caravanning) and from a bit of Googling, I can see the engine has effectively gone into 'limp home mode' with various suggestions that you need to take the van for a good hard run to clear the soot built up in the filter.  I was slightly surprised by that because we had only recently come back from Cornwall (I live in East Sussex), so the van has had plenty of recent motorway driving in last few weeks.    Is this a genuine fault and one I should get a mechanic to look at, or is it something that regularly occurs and simply needs a good drive to clear out the filter?  I'm reluctant to go too far at the moment in case something is failing and breaks down, but equally I don't want to put it into a dealer for servicing if it isn't a proper fault.

Seeking advice / guidance / opinions?