While I would love to have a list of all bioinformatics in europe myself (as I am looking to start at PhD program myself next year), I fear all I can tell you that there are too many to list them. I am not sure how you would discriminate active and great research (much used?/novel topics, I mean research has always a reason and whether it is interesting depends upon you). Anyways, there are probably many hundreds of Groups in Europe nowadays in different fields of Bioinformatics (alone here in Heidelberg, I would estimate about 100 pure individual Bioinformatitions and several dozen computational biologists). I would recommend to look up People here on Biostar where they say they come from or look at the location of publication authors or tool developers.
This might help you http://rsg-uk.iscbsc.org/resources/14-academic-courses-uk.html :)