Hi and welcome to the forums.
That's a strange combination of components you have selected and there is some very good advice given already.
The most important one to address is the memory. Ryzen loves/needs fast memory. If you go with 2400mhz memory you will be crippling the CPU. For Ryzen you should be looking at 3200mhz DDR4 or faster and the tighter the timings the better.
The A320 motherboard is just too cut back and lacking in my opinion. I would be aiming at a minimum of a decent B450 board to get the best out of the CPU and memory.
Don't go with one of the CPU's with built in graphics when you are going to have a proper graphics card as well. The 3100 already suggested or even a 3300X would be a much better buy. Shopping around may even find you a bargain for £120 or less. Just remember that you can always change the CPU for a better one further down the line.
Cheap PSU, just no!! Saving money on the PSU is a false economy and should be avaioded at all costs. Buy cheap, buy twice has never been more true when it comes to psu's. A cheap one will have the lowest quality internals, be innefficient and will have vital safety features missing which means when it fails it will most likely take out one or more of your components with it. If your choice is indeed the one on Amazon then you couldn't have picked much worse than that. If you choose it based on Amazon user reviews then you are looking at things the wrong way when it comes to PSU's. All the average user can post in a review is if it works or not and if it's quiet or noisy. They won't have the expensive equipment required to properly test a PSU and certainly won't open it up to see the quality of the internal components so ignore user reviews completely when it comes to PSU's. You won't find any professional reviews on cheap PSU's such as this because at the end of the day they are garbage that shouldn't even be considered. Take the one you have selected for example (if it's the Amazon one). That so called 500w psu only has a pathetic 216w on it's 12v rail where the power is needed and to be honest I doubt if it would even manage that. A modern PSU should be able to deliver all or near enough all of it's power on the 12v rail(s). Add to that the fact that they are well known for exploding and killing other components and it should be avoided. Always buy a quality PSU and it will last you through several upgrades. Aim for one that is Gold rated and have a minimum of a 5 year warranty although 7 year and 10 year warranties are quite common these days. You have the Bitfenix Formula series at the budget end which would be the minimum Gold rated units I would recommend. If the budget is really tight get a good quality Bronze rated unit although there isn't that much of a saving over the Gold rated Bitfenix Formula's for a decent Bronze rated unit so personally I would bite the bullet and go Gold.
Cheap case. By all means get a cheap case, it's one place that is realistic to save money without having a big performance impact. In fact some cheap cases such as the Kolink ones on OCUK are very good and have some nice features. Ones to avoid would be cases that mount the PSU in the top and ones that have a single or no inlet fan and only a 80mm exhaust fan. If the one in your list is the CiT Pyro then it's not a bad case at all and has space for 3x 120mm at the front, 2x 120mm fans in the roof and a single 120mm fan at the rear. The PSI is mounted in it's own compartment in the bottom as well. Searching around can find it for £32 though.
Cheap SSD. Be careful with these Chinese SSD's. While they seem to be very good value for money they can fail quite quickly and often have to be returned to China and can take a long time or get lost in transit. If buying from Amazon make sure that it's sold by and fulfilled by them so that should a failure happen you only have to return it to them. For peace of mind I would rather stick with a known brand and you can get Sandisk, PNY, Western Digital (WD), Gigabyte and Kingston A400 480MB drives very close to the price of the Asenno.
