Upload via Bluetooth module - Any help Appreciated

Not sure if this is the right place exactly so Mods please move if appropriate.

It's not a standard Arduino issue.

I have a bare bones set up on a Breadboard (ATMega328P-PU with Arduino Uno Bootloader).

I have a HC-05 based Bluetooth module on a breakout board and I was thinking there shouldn't eb any reason why you can't upload sketches just like with regular USB>TTL.

So..I've got the BT module set up on the Breadboard and it's Paired with the PC and installed as COM8 and COM9. I can use Tera Term with COM8 and do a loopback test fine (with RX/TX pins of BT module shorted on the breadboard).

I've replaced rtxserial.dll with the fixed version for freezing menus etc. (just in case it has any bearing).

With The port released and IDE up, I can get tot he point of compiling the sketch, do the manual reset at the MCU and then see the BT module light go solid for a split second as avrdude connects. Then it fails with the following message:-

avrdude: ser_open(): can't open device "\.\COM8": Element not found.

That's where I'm now stuck.

I'm convinced this should be possible. What am I missing?

Thanks in advance for your time.