That ECU has a 95P08 EEPROM, and it has a resistor on the back side that makes it difficult to go into boot mode without removing it. I would post a picture of the resistor on the back side, but the site is so slow these days it would time out trying to post my comment. So here is the link:
Picture of resistor on the back of the ECU: https://i.postimg.cc/MZt6xVDk/VAG-ME-711-platine2.jpg
If you remove the 0Ω resistor on the back side of the ECU, it will go into boot mode every time without issue; however, you lose all port flashing and diagnostics, so you will need to put it back on after you are done.
You need to have a bench flash setup with the following pinout: https://i.postimg.cc/6qZF7sv0/505830917-10233036365946216-3479748955704475688-n.jpg
Once you have your full bench setup, you will want to have the software loaded and the ECU, cables, and laptop all connected before attempting to put the ECU in boot mode. In order to put the ECU into boot mode, you need to have pin 24 earthed/grounded while applying power to the ECU. Leave pin 24 grounded for approximately 3–5 seconds. Make sure you have the correct COM port and EEPROM layout selected in the software before attempting to read out the EEPROM.
After you have an EEPROM readout, now you need to get into a hex editor and flip 4 bits: https://i.postimg.cc/Sskn1qyj/k-Xdl-Pe6.png
Once you do that, you will need to put the ECU into boot mode again and write it back to the ECU. Do not forget to reinstall the 0Ω resistor. You can test the ECU in the car before reinstalling the resistor to verify you have disabled the immobilizer, but if you do not put it back on, the ECU will not have any more port communications.
You can use FlashDock—it's a full boot mode suite I made that handles EEPROM and one-click immobilizer off with checksums. It also does boot mode flashing for bricked ECU recovery, or if you want to flash or read in boot mode: https://mega.nz/file/NcIWnZIR#mmyKp3rkOYbVtxSD0OPzNV_eoIz5ATn8NVwox53dkC8

I managed to get the resistor off it was stubborn to remove. Im guessing it doesnt matter which way round the resistor goes when i do go to refit it?

I've tried many times to get it into boot mode with no success

Hi what port should it be on or does it matter. I'm on your program at the moment. I carnt see the settings for latency and time out probably where I'm going wrong. I put pin to ground at pin 24 then turn the power on then remove ground after 5 seconds then I click on your program

Kind regards