I would recommend looking at the Hilook range from Hikvision. It's Hikvisions lower cost solution for domestic and small business applications. Don't risk buying Hikvision from eBay, it will be from a non authorised source and you are unlikely to get any warranty. We have found the Hilook stuff to be spot on price/reliability wise for small jobs. If your not a trade installer you will probably find it difficult to buy Hikvision as authorised re-sellers wont sell to end users so this is the next best thing. I would recommend this camera as it has a good night vision range https://connectec.uk/security/cctv/cctv-cameras/diy-analogue-cctv-cameras/hilook-thc-t240-m-4mp-tvi-turret-camera?variant_id=13110#variant-details
I would avoid using dome cameras outside as they suffer quite badly from infrared bounce back when the dome cover gets wet or dirty and the night vision ends up being really poor. Look at the turrets or bullets.
If you can stretch to an IP system you will get better image quality and a much neater install as the cameras run off a single ethernet cable and power from the recorder so there's no messy power supplies etc back at the recorder end. You get all the usual app access on your phone.They have a really good deal on a 4mp IP camera at the moment that has a cracking image. https://connectec.uk/security/cctv/cctv-cameras/diy-ip-cctv-cameras/hiwatch-ipc-b140-4-megapixel-hd-compact-ip-bullet-camera
The Hilook recorders will usually display 4x 1080p cameras at once which is all you will really need when split in to 4. With higher resolution you will benefit from a better quality digital zoom on playback.