I owe 1400 pond on court fines now law officer been out told me to pay 800 pound by next Friday or I will be aressted told him I can't but will set up direct debit and they
Said no what can I do

No sure of what you can do. Have you made any attempt to pay the fine? 1400 pound is a lot of money.

Is this the UK? I am surprised that failure to pay one's debt is still (apparently) a crime. Is it really true?

This isn't a debt but a court FINE, and Yes you can be arrested and jailed if you fail to make payments, as this is a criminal matter.
All this information is laid out in the original judgement, including the payment terms.