Is there much to see in and close to Alta i.e. is it worth staying the night just to break the long journey from Nordkapp back to Tromso region (driving). I.e any local walks to enjoy midnight sun over water etc. This is for a night in 2nd part of June. Thanks, Lee.

Thousands of prehistoric rock carvings just outside town, a Tirpitz museum if you are a WW2 buff, the Alta canyon, and world class salmon fishing. A short hike up Komsa hill will give you a good view of the surroundings and the midnight sun.
Other than that there isn´t much to do.
Btw, Nordkap is a tourist trap.

Many thanks. The Alta Canyon sounds quite good, especially if there's any walks around the fjord etc. and a chance to see the midnight sun over water etc.
Going to stay in Honningvag the night before, but do the hike to Knivskjelloden (if I can spell that) instead, the true furthest point north (and much quieter).