Hi Julie
I did this trip in March and my advice would be - don't hesitate - book it!
You will have an amazing time. The people are hugely friendly, the food is incredible and the views....well...wow!
Suggestions - get some YakTrax to put on your shoes because it can get a bit icy and slippy when you aren't in central Reykjavik. Don't bother with an umbrella because it can get so windy that you will never keep it up! Take a waterproof jacket and plenty of layers. The weather is incredibly changeable - they have a saying "If you don't like the weather in Iceland, just wait five minutes" and it is absolutely true!
Drinks are pricy but the hotel has a happy two hours 🙂 There is also an ATM in the reception so don't worry about changing currency. Don't forget to take your swimming gear because a dip in the Blue Lagoon, and also the local swimming pool, is a must.
My only disappointment on the trip was that our helicopter ride was cancelled at the last minute because of the weather but, this gives me a great excuse to go back, which I certainly intend to.
Happy to answer any other questions that you may have
Mandy