The museum is split into 3 sections, first of all you enter and have the overlord embroidery. This is dubber as the modern day Bayeux Tapestry and depicts the events leading up to and including the invasion. The embroidery is displayed beautifully and is absoultly fantastic. Then there is the cinema. This is a 16 minute film that runs every 20 minutes. It is about the propoganda and build up to DDay, using videos from the Imperial war museum. This is a really good way to start, so I would recommend watching this before viewing the embroidery because it helps set the scene of the museum.
Then on the other side of the museum is the actual museum. It was redone a few years ago and is visually very appealing. There are fantastic displays and artefacts, with various videos and local portsmouth people recalling memories coming from the speakers. Which really brings it all to life. However, one if the highlights is the vehicles shed you walk through, with Tanks and carriers that were used in the invasion. In the carrier you can actually walk on to it, which feels very surreal.
One of the highlights of my trip here was talking to the Veterns, who volunteer everynow and then. I got a first hand chat from two gentlemen, which as you can imagine is an invaluble addition to the museum. They were happy to answer questions for hours!!
However, the downside of the museum is the cafe. There is a small cafe at the back of the museum run by a catering company called Yellow Kite. The food is very expensive and nothing special. It was a very sunny day when i visited also, and because the museum is on the seafront the cafe was heaving and i had to wait 30 minutes for a toasted cheesy!! So, I wouldn't recommend eating here.
My personal recommendation would be to make a day trip here in the morning, and then when youve finished walk out the back cafe doors and into the castle grounds. The castle is free and also run by Portsmouth Council, so when you pay the £6.50 entry fee for D-Day, you could have a full day out for that price. Southsea castle is very small behind so I wouldnt recommend it by itself, but if yuo are visiting the D-Day, then I would definatly say it would enhance your visit to Portsmouth to pop in!