<Pedant mode enabled>
EU doesn't make "law" (that people or organisations have to comply with), it issues Directives which Member States are required to transpose into national laws. This is why, for instance, there are huge differences in health & safety law across UK and EU, despite being all being crushed by the same iron fist of Brussels*
So both statements could be right, in that the Directive might have said "minimum 2 metres" (or refer to a regulation that specifies this). Or it may be something more qualitative e.g. "high enough to deter trespass" and based on that, the UK government came up with its own number.
*JOKE - please let's not start re-litigating Brexit!
Back on topic, I think electrification of EWR, rather than a standalone scheme, needs to be thought about in the light of other developments that make it cheaper or more sensible
i.e. I don't think you'd do it until after Oxford area. National Grid may also be able to provide additional capacity at 25 kV at Quainton, beyond what HS2 have applied for.