I don't think it is. (1) I've been watching a lot of Lovejoy lately, and tho the voice has that same quality of tone, etc, something - for me anyway - is missing. And (2) why would they do it? - if you are going to pay a well known name for a voiceover, chances are you want the voice they are known for, and if they wanted someone Irish, surely they would get someone Irish.
I am sure I have heard that voice elsewhere too - maybe Craig Doyle from Holiday - but I tried to find out for sure and got nowhere. I couldn't get any info on the Magners site either.