Naval Base, Devonport.

This is an operational base, so you can’t just turn up and have a look round! However there are a couple of ways of getting to see parts of it. One way is to apply for a place on the frequent guided tour (twice daily, several days a week). This could include a submarine or warship visit. They’ll let you know if your application is successful. You might want to enquire what you should bring with you, to avoid a panic attack on the day on the lines of “where’s my photo ID?!” I can’t tell you if they’ll run a security check on you or not…
It would be a good idea to check beforehand the location of the meeting point and how to get there. Devonport is a big place… Once you have located the meeting-point on the day, you should be able to park in front of the reception centre, assuming the armed guards let you in.
Another way of getting in is to wait for one of the Navy Days or Heritage Days, when you can just turn up and look at various museums, and go on timed minibus tours of parts of the site. This might include a submarine or warship visit, and historic buildings.
A note of caution: I don’t mean to be rude to the overweight and disabled, but for visiting warships and submarines, a certain standard of agility and fitness is required. Operational vessels have steep ladders and confined openings.

Tintagel Castle, Cornwall

English Heritage
The site is encrusted in Arthurian myth. In reality, dramatically sited low walls are all that remain of a 13th century castle. Some parts of the site have succumbed to sea erosion. The remains extend on both sides of a gorge that separates the headland from the mainland. Castle aside, it’s interesting to wander around the headland, which is littered with ancient remains. There are sea views.

View from Tintagel Castle
View from Tintagel Castle

Old Post Office, Tintagel

Tintagel old post office Front
Tintagel old post office
National Trust.
The brief use of the building as a former post office is incidental. The building, originally a yeoman’s farmhouse, dates from the 14th century, and with its wavy roof that seems to be sagging into the earth, it looks its age. Interesting building with old furniture and displays, and a pleasant cottage garden.
Tintagel old post office-Rear
Tintagel old post office-Rear

Pendennis Castle, Cornwall

English Heritage.
The castle was built as one of Henry VIII’s coastal gun forts, and the site continued in use as a military strongpoint up to the Second World War. Besides the original castle, the site includes substantial stone-built barracks buildings from more recent times. Suggested visit time: about 2 hours. There is plenty to look at, with sea views, and you could also take a boat trip across the estuary to visit St Mawes castle nearby.

Portsmouth Historic Dockyard

This is a large area with several major attractions:
HMS Victory – probably too famous to require any further comment from me.
HMS Warrior – a fascinating survivor from the era when the Navy was changing from wooden sailing ships with broadsides to steel dreadnoughts with turret guns. She contains features from both the sail and steel eras. Personally I found her more interesting than the “Victory”
Mary Rose – a famous early wreck raised in 1982 in full view of the television cameras. I found that viewing the ship – or rather its surviving half – was something of an anti-climax. Currently it’s not on display (Sept 2011), but there are historic relics and museum presentations to be seen in the Mary Rose museum.
National Museum of the Royal Navy – I remember that there was so much stuff in here that I left without going all the way round. No doubt it’s been re-organised since my visit, and they now recommend allowing 1 ½ hours to see the four galleries.
The Harbour – Boat trips, obviously.
“Action Stations” – aimed at active youngsters.
Note that admission to the various Historic Dockyard attractions is now by one all-inclusive (and inevitably rather expensive) ticket. For terms and validity, including re-visits, see the website. Note that each major attraction also has its own website. To get maximum benefit you might need to spread your visit over more than one day.

St Mawes Castle, Cornwall

English Heritage.
One of the best-preserved of Henry VIII’s coastal artillery fortresses. It is built in an interesting clover-leaf shape, and has been little altered. Be careful of headroom when exploring the upper parts – I banged my head so hard it felt like my neck had become shorter :-) It can be visited in conjunction with the larger Pendennis castle nearby, if you make a harbour ferry trip between the two.

Stondon Motor Museum, Beds.

A large and diverse collection of motor vehicles, from 1900 to 1990. Well worth a look if you are interested in viewing a large car collection.
They also have a full size replica of Captain Cook’s exploration ship “Endeavor”. The replica, designed to “enable children today the unique experience of seeing life as it was on these primitive ships”, is constructed of sheet plywood, and does not replicate the full hull depth. So if you are expecting a replica of authentic frame and plank construction, looking ready to put to sea, this isn’t it.