The world is your oyster here. However for a nice not-budget but still very cost effective and decent enough kit I would look at the Hikvision stuff. Only problem is they are Chinese so maybe not so ideal any more.
For some still decent enough kit and pretty cost effective a CCTV disty we have used in the past have plenty of options and can offer some advice. They are trade only normally but I suspect at the moment they will likely make some exceptions. They do their own SPRO kit which is fine in my experience.
https://www.luxritesecurity.com/
They are Stevenage so not that far from you and will ship by courier anyway. Just say Dean @ Rock IT Services gave you their details.
The best option would be IP camera's really just running some CAT5e to each camera with no power needed as the PoE network switch will supply power as well as data. You can get 4 channel or 8 channel or more if you need more cameras. Just connect to your Internet router with an Ethernet network cable and most have web or Android/iOS mobile apps to view. You need a Network Video Recorder (NVR) and all cameras centrally cable back to this. Most have an embedded PoE switch to connect all together and supply power over the same CAT5e cable. You can buy the NVR's with or without disks and install your own depending on what size you need. You need to calculate resolution, frame rate, length of time to hold footage etc. x how many cameras to get a total storage requirement. There are loads of good calculators on the web.
The non IP cameras are a bit cheaper than the IP cameras but use coax cabling or converters. The IP stuff is much easier and not much more expensive. Also gives much more flexibility for any future moves or changes.
Night vision can be variable with some better than others. The issue is a good day camera won't be good at night and a good night camera won't be good in the day. An additional IR illuminator can help if night vision ends up being poor. Or a security light can help as long as it isn't mounted directly above the camera. Just below is good. Mobotix are an expensive German make and their take to get around this is dual camera units with day camera for day and night camera for night! That is quite high end though really.
I wouldn't go wireless for many many reasons.
I am just about to install a new Paxton 10 in my place which is great and integrates all the electronic door access control with CCTV in a nice single platform. We have a Salto door access control system here at the moment that the Paxton 10 system will replace as we prefer Paxton to Salto now. It isn't silly expensive but isn't cheap.
CCTV is not my day job but we are so broad we have installed a fair bit of CCTV over the years and always get involved in integrating it into the customer's network/infrastructure.
Feel free to ask any questions and happy to help where I can.
