I don’t quite understand why the method of escalation from your provider to Openreach has any affect on you. You just want your line installed, and as quickly as possible. 🙂 Can’t figure out why they’ve even mentioned DSO to you!
DSO escalation is one of the top levels of escalation within Openreach that providers can utilise, given the issue fulfils a certain set of requirements.
The difficulty you may have is that your issue involves third parties. Have Openreach actually spoken to the HA and LA? Either they haven’t (so escalation should see progress) or they are waiting for HA / LA approval to return. Escalation rarely helps here as its out of their hands. Is it for a road closure?
If your near area’s of flooding this probably isn’t helping your cause, they’ll be treating them issues as top priority. Although 6 months is taking the pee a little. (I have seen longer however!)