You can't find free English courses anywhere unless you are in very special circumstances, such as an asylum seeker, in which case you will be advised on whether there are courses available. The only other way that free courses are sometimes available is through the local Jobcentre if you are long term unemployed; it may be possible to get help with basic English, literacy and numeracy, but courses everywhere are being cut.

If you are simply trying to improve your English, there are no free courses - how would the teachers get paid? The cheapest option may be Adult Education. If you scroll down the English course list you will see several ESOL courses, and if you follow the links you will find details about fees.

Otherwise, you could try asking for local tutors on Gumtree - people will often give private lessons quite cheaply, especially if you look for lessons on Skype. You can find one example here but there are plenty of teachers advertising lessons.