On the way back you may have problems transiting via Frankfurt, as there are direct flights available.
https://www.auswaertiges-amt.de/en/coronavirus/2317268
Citizens of EU
member states and their families, as well as citizens of the United Kingdom, Iceland, Liechtenstein, Norway and Switzerland and their families are allowed to travel through Germany to reach their home country if no other travel connection is possible. They will also be allowed to enter if their home or legal residence is in Germany. Other people may be rejected entry, if they cannot provide proof of urgent reasons for their entry. Please refer to the Federal Ministry of the Interior, Building and Community for details.
Here is a useful list of entry restrictions:
https://www.iatatravelcentre.com/int...1580226297.htm
There is also a reasonable chance you would need to quarantine yourself for 14 days when you arrive back in the UK (not currently required, but discussed).