I agree with Jonathon, a true Scottish yeast can throw a hint of smokey phenol into the beer. I have experienced this, but have not deciphered what conditions that yeast wants in order for it to create that phenol. Some brewers try to cheat and use a smoked malt of some form to add the phenol, but I haven't been impressed with the result. I can tell you that achieving that phenol in conjunction with the characteristic Golden Promise sweetness is a beautiful thing.
In the case of an ESB that is likely to be more hop focused, I'm not sure you would pick out the phenol. In addition, I'm not sure that it would be a positive addition. However, if its reserved and melds well with the other malt and hop components, it could be fine. Do be on the lookout for excessive phenolic character. That will likely be dinged in judging.