The problems with Exams is that they are not real world scenarios. If you were going to EGHH because you NEEDED to go, then maybe Southampton might be a fine alternate. If you are going for training, then I'd just go home.
What are the rules with regards to Alternates? If the destination is forecast to be VFR then you don't even need to file an alternate right?
As a general rule, I'd file an alternate which has a different climate, so SOU and Bournemouth are not good, because if the weather is crappy at EGHH then it is likely to be crappy at Southampton too. You'd be better off filing Boscombe Down as it is inland, or I agree with you Lydd or Southend as they are likely to be in a different air mass if there is frontal stuff coming in from the SW (plus you have the chance to check Shoreham on the way past and dive in there and just go home for a beer if weather permits).