Informing Farnborough that you were leaving the frequency briefly to call Rochester info, would be an option. However, you do not appear to be particularly close to their zone, and in good VMC, a keen look out is all that is required. Also, if you have requested a Basic Service from Farnborough, they would keep you informed of other traffic if not too busy on the frequency. However, the resposibility is always yours to see and avoid in VFR flight. I would monitor Rochester frequency on the other radio, if you have one, and if the chatter indicates lots of activity, then it would be a good idea to give them a courtesy call. Hope this helps.