There's an analysis of ablation complication rates at US centres:
medscape.com/viewarticle/91...
which shows that the rate of complications is much higher at low volume centres.For instance over twice as many strokes and five times more cardiac perforations.
Most of the centres have very low numbers of ablations - over half doing less than 10 a year, so I don't think the results are directly comparable to the UK where I believe volumes are higher? Nevertheless it does show how important experience is in choosing an EP/centre. I would want expect an EP to carry out at least 50 a year. For instance, my EP Prof Richard Schilling carries out more than 150 ablations a year.