Are you already in receipt of the Self Assessment form from Hector over there in Cy? If so, fill it in quick and send it back to HMRC via DHL or similar.
If your form is at a UK address, can they get it scanned and email it to you sharpish?
If neither is viable for you, then online by 31 Jan 2018 it must be. We don't want you getting an automatic £100 fine for late delivery! Here is the main HMRC link to get going:
https://www.gov.uk/topic/personal-tax/self-assessment
It's a very secure system, so initially, you have to set up an online verified account with them. Not much different to signing up with eBay, PayPal or Amazon, really. In fact, maybe easier, LOL!
HOT TIP: Sort this out online before the end of October. Then, you can sit back, chill, and focus on your Christmas and New Year festivities! Without worrying about those bloody parasites at HMRC (who have never done a single day's productive work for the lifeblood of the UK since the day they left school)
Good Luck- and get back if you're stuck please- AL

Gone but not forgotten...