I had the same issue with my Clio Grande (if this is the car in question) a fair few years ago, ending up just needing a new cylinder,
BUT.... becareful about taking off the hub and playing about inside as i attempted this and incurred all sorts of issues, not only did i need a new cylinder after fiddling but a new spring kit (after taking the shoes out to clean the fluid from them), and there was also some type of seal thing that got knackered by taking the hub off cos the brake fluid had eaten into it by leaking,
Car eneded up being sat on the side of the road for a few days until i could get it towed to a garage for fixing, ending up costing me more hassle than it was worth,
My advice would be to just take it to a garage (IMO) to get it looked at so its already there and anything it needs they can get !!