If you move to France or any other EU country, your insurer must pay your supplementary pension scheme the same amount and under the same conditions as if you were living in the UK.
In turn, French law may not discriminate against your occupational schemes from the UK, e.g. by giving French schemes preferential tax treatment.
NO — Germany should not claim back your tax rebates simply because you retired and moved to Greece. It is against EU law for an EU country to have rules that deter you from moving around in the EU. If Germany does so, that will in effect obstruct you from exercising your right to retire to another country.
In case of problems with national authorities, you can get help here.