If your interested in subs/nuclear then round bristol/bath way has plenty of engineering. With the likes of bmt, babcock, Atkins, frazer Nash all having offices here as well as all of the support companies. Not to mention other defence companies like airbus, rolls royce, ultra, Ge. Being close to abbeywood helps as that's the main MoD procurement center so most defence companies have a presence near even if the main sites are elsewhere.
If you've not done a placement yet can well recommend trying to get one where you would like to end up , as pretty much all the placement grads who later applied for jobs got them.