Infraviolet:
- Can only ATMEGA328P chips such as https://uk.rs-online.com/web/p/processor-microcontroller-development-kits/7589339/ be used, or can any ATMEGA328 do? I've found the latter available cheaper by a few £, which matters when you need quite a large number of them.
That one comes with the bootloader installed, which allows you to upload sketches to it over USB-serial just as you do with your Uno. If you buy ATmega328P without the bootloader installed then you only need to connect an ISP programmer to the chip and then do a Tools > Burn Bootloader in the Arduino IDE to flash the bootloader to the chip, after which you have the exact same thing RS is trying to sell you at a steep markup. You can use your Uno as an "Arduino as ISP" ISP programmer if you like or you can buy a dedicated ISP programmer, which is more convenient if you'll be doing a lot of this. I like the 6 pin USBasp programmers. You can buy them for as low as <$3 USD w/ free shipping on eBay if you don't mind waiting for shipping from China.
Infraviolet:
2.Assuming that a 16MHz oscillator and a pair of 22pF capacitors are used is an ATMEGA328P (or 328 non P if that is possible, see Q1) able to be programmed just like a normal uno in terms of settings or must breadboard arduino settings be used? The same goes for the process of putting a bootloader onto the ATMEGA, must weird settings be used?
You can just treat it as an Uno.
Infraviolet:
3.When wiring it up to program I've found that one takes an uno board, carefully levers out the ATMEGA (any tips on technique and tools for this?)
I use one of these:
I only recently found they're not intended for pulling DIP ICs from a socket and it is kind of awkward but I still use it. The trick is that if one end of the chip comes loose from the socket before the other then you will bend a bunch of the pins. After they're bent they lose some strength and you will have trouble getting them in a socket without bending them again, losing more strength until they eventually break off. Ideally you would not use a standard socket for a lot of insertion/extraction cycles. They're not really intended for that purpose. My advice is to leave your Uno alone and instead just buy a cheap USB-TTL serial adapter board that is made for this specific purpose. Make sure to get one with the FTDI header pinout that has the DTR/CTS pins broken out. It's also nice to get one with adjustable 5 V/3.3 V power. I use these:
https://www.ebay.com/itm/253506053642
You just need to know that the FT232 chip on them is counterfeit and the official FTDI Windows drivers were at one time bricking counterfeit chips. I don't know whether they are still doing this and there are easy workarounds for the issue to fix the "bricked" chip.
Another option, which won't have the bricking issue is this one:
It's not so easy to change the power level on that one.
Infraviolet:
Are the oscillator and capacitors supposed to be fitted while doing this?
When you do Tools > Burn Bootloader you set the fuses according to the hardware definition of the board you have selected in the Tools > Board menu. If, as with the Uno, those fuses specify an external clock source and you don't have an oscillator connected then the chip will be "bricked" until you connect an oscillator. You also have the option of running the chip at 8 MHz or less on the internal oscillator but you need to use the hardware definition for it. That's the point of the "breadboard" hardware definition you mentioned but I recommend using this one instead:
Infraviolet:
4.With a lone ATMEGA328 chip will I2C work exactly the same as with a full uno?
There's no magic to an Uno. It's just an ATmega328P on a PCB with the minimal support circuitry. You can find the schematics here:
Infraviolet:
5.Are there any safety circuits on an arduino to prevent damage which are not built into the ATMEGA328 itself, if so what extra pre-cautions need to be taken to avoid burning out a raw ATMEGA chip which aren't a worry with a full arduino?
There's a PTC fuse and some power switching circuitry to prevent problems if you have power connected to the barrel jack and the USB socket at the same time. I suppose you could consider the voltage regulator on the barrel jack a protection of sorts since it will prevent the chip from >5 V supplied to the barrel jack.