In theory, the cheapest I could do whilst trying to meet your criteria would be something like this:
PCPartPicker Part List
CPU: AMD Ryzen 5 2600 3.4 GHz 6-Core Processor (£108.00 @ Amazon UK)
Motherboard: MSI B450 TOMAHAWK MAX ATX AM4 Motherboard (£89.99 @ Box Limited)
Memory: Patriot Viper 4 Blackout 16 GB (2 x 8 GB) DDR4-3200 Memory (£56.90 @ Ebuyer)
Video Card: PowerColor Radeon RX 580 8 GB Video Card (£143.45 @ Ebuyer)
Total: £398.34
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-12-24 19:02 GMT+0000
Keep in mind that with this configuration, you will be able to do all of the things you've mentioned (given that you're gaming at 1080p) quite comfortably. I didn't go for cheap but for good budget options.
Now, you've mentioned that you want to go as cheap as possible, the issue is that if you're updating your build, you will need to buy a CPU, Motherboard and RAM at the same time so it's hard to recommend anything lower. Especially if you're planing on upgrading the CPU later on, you don't want to go for a cheaper board/RAM.
Which brings me to my second recommendation. Your CPU is a Quad-Core CPU that can be Overclocked to 3.8Ghz. It can actually hold its weight in gaming well enough and can be considered sufficient for multimedia, blender and photoshop. So you could simply go for a GTX1660 Super:
https://uk.pcpartpicker.com/product...-xs-oc-video-card-gtx-1660-super-ventus-xs-oc
Or even a 1660Ti for another 30-40quid.
This would cover your all your needs as well as your gaming needs for years to come. You can then upgrade the rest whenever you're ready to spend a bit more.
How does this sound to you?
Also, which model is the Gold EVGA PSU