They were originally Folland, then Aerostructures and are now part of GE Aviation. They made a lot of subcontract parts for Harriers and Hawks and there is a former Red-Arrow gnat outside on a pedestal at the corner of Hamble Lane. The original seaplane slipway is still there at the bottom of Ensign Way.
I was in my Mirror dinghy in Portsmouth Harbour the day that the Invincible came back from the Falklands. Once she was safely tied up alongside her Harriers took off, circled and then headed west - to Yeovilton, I believe. What a day that was!
http://en.wikipedia.org/wiki/Folland_Aircraft