Charming town, great for those with an interest in the sea and maritime history or underwater archaeology. It's worth the trip to see the Mary Rose and the HMS Victory. There's scuba diving at Horsea Island, where you can see the Elizabethan merchantman, but this is in only 6m.
Portsmouth is not a big town at all. It is divided into three parts -- city center, Head Interchange and Southsea (Portsmouth Southsea Railway station is located in city center but not Southsea). The Portsmouth hostels and hotels are mainly located in city center and Southsea. Obviously if you can find a bed near Head Interchange, that would be very nice.
Head Interchange is where the main attraction of Portsmouth located. You can find the designer outlet and the Royal Navy historical dockyard there, which is worth seeing. Your ticket is valid for one year from the date of purchase, so you can return at any time to visit the attractions -- no need to rush for the attraction. The Portsmouth Harbour Railway station is also next to the interchange. If you want to go to a hostel in Southsea, you may need a bus (number 6, 6A) to take you there from Head Interchange. It is also possible to walk there from the interchange -- it takes about thirty-five to forty minutes to get there.
If you want to get a supermarket in Southsea, there are two small supermarkets in Plamerston Road. However, the Iceland store over there closes at 6 p.m. If you want to get to a bigger supermarket, you may need to go to the city center. You can find a lot of restaurants in Southsea, Head Interchange, and the city center. There are also some restaurants located inside the designer outlet as well.