Remap should be fine mate, just make sure you keep on top on maintenance. Stage 1 is about 230-260hp depending who does it. The more aggressive the map the higher the wear on clutch etc.
If you get rid of the pre-cat and fit a larger downpipe you should free up some power, but the main cat (the one that actually matters in the uk) remains in place.
I would take it to a reputable tuner, such as R-tech or a good Revo/APR dealer and they should perform a health check before mapping.
Mine was mapped before I bought the car and that was about 30k miles ago in Feb 2014. The problems I have had so far appear to be those that affect all Leons, mapped or stock, so my experience is get it mapped