I have a Clio of the same vintage with the dCi 80 engine, which I bought new.
The car has done 99,000 miles, virtually trouble-free. The only (very recent) issue I have had is with a pair of faulty keys, which I have now replaced for the horrifying sum of £271.00. These key/immobiliser issues are very common, I believe, as are problems with the airbag and service lamps lighting together on the dashboard.
The engine itself has been completely reliable and continues to deliver around 70 mpg. While it has cost very little to fuel, it has been quite expensive to service, but I don't think I can complain much given the reliability.
I haven't really heard of serious
issues with the 1.5. It is a very reliable and proven engine which should give you many years of service.
I have ordered a new Clio, in fact, having been delighted with my existing car. Purchase a dCi Modus with confidence - you should not be disappointed.