Southern Britain was German in pre-Roman times ?

[Conal]

I. All Gaul is divided into three parts, one of which the Belgae inhabit, the Aquitani another, those who in their own language are called Celts, in our Gauls, the third. All these differ from each other in language, customs and laws. The river Garonne separates the Gauls from the Aquitani; the Marne and the Seine separate them from the Belgae. Of all these, the Belgae are the bravest, because they are furthest from the civilization and refinement of [our] Province, and merchants least frequently resort to them, and import those things which tend to effeminate the mind; and they are the nearest to the Germans, who dwell beyond the Rhine , with whom they are continually waging war

As far as I can see, Caesar says that all the tribes he is talking about differ in culture, and then he names where the geographical limits of their territories are. The Germans dwell beyond the Rhine.
When reading this it is also useful to remember when Caesar wrote this, and what his political goals were at that time.

It might be interesting to know what these "Germans" spoke, however. If you suggest they didn´t speak Germanic languages, what would you suggest instead?

My interpretation of that passage is that the Belgae are the same culture but less affected by contact with the Med. My interpretation is that these were conferderations of tribes rather than differing cultures.

The language thing is puzzling as it could be down to dialect

also interesting is;
Strabo says this ;

"Now the parts beyond the Rhenus, immediately after the country of the Celti, slope towards the east and are occupied by the Germans, who, though they vary slightly from the Celtic stock in that they are wilder, taller, and have yellower hair, are in all other respects similar, for in build, habits, and modes of life they are such as I have said the Celti are. And I also think that it was for this reason that the Romans assigned to them the name "Germani," as though they wished to indicate thereby that they were "genuine" Galatae, for in the language of the Romans "germani" means "genuine.""

Put simply they were saying that they were the genuine Celts ... the originators, the Celti di tutti Celti. Its not possible to say this side of the Rhine Celts that side Germans. So the term Germani when used by the ancients may have meant an entirely different thing that one might suppose.