Did my PBI and advanced PB at Plas Menai, I am sure that where ever you go you will get very good instruction. However, the great thing about Plas Manai was the fact that you are staying at the centre and can roll out of bed in the morning down to a great brkfast and then out to the slip all within 1min of each other, no driving anywhere, park the car and forget driving. They have Wifi in the bar and you are usually with a group of like minded people, who do help each other etc.
When I first went, I travelled on the train to Bangor, walked out of the station and into a taxi, within 15mins I was at reception and did the same on the return. They are also very flexible with catering and when I finished my Adv PB on the Sunday i stayed for a meal before driving back to the midlands, all sorted for a very reasonable sum.
Just my thoughts.