Hi!
I have recently done a topdeck tour of europe with my partner. We decided to go for the tour because we were not experienced travellers, wanted to do the big highlight cities and then go back and do our favourites in more depth and to work out what we liked when we travelled together.
I loved every minute of it! We got to meet alot of new friends, some of whom we will travel with in the future/stay with in other countries. We found out alot about countries and what people recommended to do/not to do/how to budget travel. It wasnt the cheapest option (eg. if you spent the equivalent money by yourself you could probably travel for longer) but it was a great introduction for us.
We decided that we will do UK and Ireland ourselves however, as it is easy to travel and we know alot more about we like when we travel, choosing hostels, locations and how to generally save money!
I would recommend choosing your travel options based on what you want to see, and how much time you have to do it in. If you want to just explore cities and not worry about bookings etc then go for a tour. But if you like to have a bit more time and freedom to change your plans then have a go yourself! You will have a ball either way :)