My husband & I are heading to Italy/Paris for the first time and just wondering whether its best to book day tours before we go, or just wait and do it there?

We are going to Rome, Florence, Venice and Paris. WE have already booked a day trip up to LOndon on the Eurostar. Does anyone know whether you get the hop on off ticket at Pancras Station?

Which type of day tours are you thinking of? Day tours that take you outside of the city? Or sightseeing tours within the city?

I'd just wait until you get to each city, unless it's some super-popular day trip tours.

The Eurostar is unique - in that the pricing varies by train and date - and is usually much cheaper bought in advance.

If you mean day tours by bus either in a city or to popular sights outside - you wait until you get there - so you can see what the weather will be like. Almost always you can just get tickets from your concierge on the day or evening before the trip.

From Rome we are looking at doing the Naples/Pompeii full day tour also we'd like to go visit Vatican city and the usual big tourist places.
Florence - full day tour to the Cinque terre & the half day tour to pisa

Paris - thinking maybe Giverny, Mont St Michel, Fontenbleu

In Rome, you can reserve tickets for the Vatican museums on their web site. Otherwise it matters when you are going and what you want to do. In high season some tours can sell out, so I'd advise making arrangements ahead.

In Paris, we've done day trips to both giverny and Fontainbleau but mont st michel would need to be an overnight, I believe