We're going in August and opted to book tours through Guru Walk instead. They're walking tours that are guided by locals, and you pay by tipping at the end instead of buying a ticket of any kind. We booked one in Dublin and one in Glasgow, and there are a ton of options to choose from. Unless of course you or someone in your party can't do that much walking, in which case bus tours are always the fun way to go to see most everything.