Roaming question in Germany

[Rockdoctor]

Last week my family was in our house in a German village. It is in a deep valley, and can only 'see' one mobile transmitter which is owned by Telekom. In the past all of our phones (all O2 apart from one Vodafone) have easily connected to this transmitter, but this time none of us got any connection.
Travelling around the area I realised that the O2 phones would only connect to O2-de, while the Vodafone mobile would only connect to Vodafone.de
Am I right in thinking that this is the consequence of the end of roaming charges in the EU? The networks seem to have massively reduced the number of roaming partner networks, presumably to save money. Will this be the 'new normal', or is it just a transitional period which will return to the old normal?
It's very frustrating suddenly to find all your phones are useless in a place you spend a lot of time.
Any idea which UK network partners with Telekom in Germany?

[MI5]

Auto network search will always latch you onto a preferred network, but you can still usually find other networks to connect to via a manual search.

[jonsie]

A manual selection should have allowed you to connect to Vodafone as well. 

Roaming partners can be found here. Your experience shouldn't be the new 'norm'. 

https://www.o2.cz/osobni/en/roaming/225561-prehled_roaming_partneru.html

[Rockdoctor]

I did try manual connecting; the phone could see all four networks, with Telekom by far the strongest. The Voda mobile would never connect to any network but Vodafone.de
Remember, I have been going to this house for years and in the past it always connected automatically to Telekom. Something has changed in the past few weeks since I was last there, and it looks to be connected with the end of roaming charges.

PS I rebooted the phone several times to see if that solved the problem - it didn't. And my wife and three kids, all with O2 mobiles had a very similar issue.
It wasn't a problem just with the transmitter in the village because none of the mobiles would connect to other networks elsewhere either.

[MI5]

Who knows what devious plans the networks have dreamt up to get round their additional costs but no doubt we will all find out sooner or later.