Lowestoft has no harbor, It does have the Walls icecream factory right on the coast (been there once) so you can get the crew some icecream
historically it had a destroyer flottilla and several squadrons of Torpedoboats, since it's the most easterly port in Britain
If you go near there, be aware lotsa interesting spiky balls that go boom in that area.
The next harbor would be southend
good hunting