Well I've now tried a Fatboy and a slim but didn't really get on with either of them. I found them too mild on the low settings and not smooth enough on the high settings. I didn't experience any nicks or irritation, I just didn't enjoy the shaves from these razors.
However, thanks to the suggestions of forum members I have also tried a Slant and two open combs; a New and a #15, all purchased through this forum. I much prefer the shaves that I get from these razors in terms of both comfort and closeness. I think I'm going to start selling off the milder razors that I have accumulated and I might move on to try a Joris or Muhle r89 head next.