Thank you for your suggestions. Here are some more sentences I'd like you to check.

1)On leaving school (After leaving Eton), Orwell served in Burma for the Indian Imperial Police.
2) On his return to England he experienced poverty at first hand. As a matter of fact, he sought the company of down-and-outs (I need a synonym) to find out how institutions for the poor worked.
3)In particular, he took (started) to wearing second-hand clothes and he lived in commom-lodging houses in the East End.
4)After working for a short time as a dishwasher, he began publishing his works under the pseudonym of George Orwell.
5) He chose George because it had an Englishness about it (can I rephrase it with: because it sounded English) and suggested plain speaking and common sense (?).
6) He chose (?) the surname Orwell from the name of the river he was fond of. (or of which he was fond).
7) In 1936 we went to Catalonia to report on the Spanish Civil War.

1) After leaving Eton, Orwell served in Burma for the Indian Imperial Police.

2) On his return to England, he experienced poverty first hand. As a matter of fact, he sought the company of destitute people to find out how institutions for the poor worked.
(You could also use "impoverished" instead of "destitute.")

3)In particular, he began wearing second-hand clothes and lived in commom-lodging houses in the East End.

4)After working for a short time as a dishwasher, he began publishing his works under the pseudonym of George Orwell.

5) He chose George because it sounded very British and suggested plain speaking and common sense.

6) He chose the surname Orwell from the name of the river he liked.

7) In 1936, we went to Catalonia to report on the Spanish Civil War.