Good News
Acer UK have replied to my email and the result is your motherboard is a standard board and can be moved to a new case.
Their e-mail is below:
Thank you for contacting Acer UK.
We regret the inconvenience experienced.
Regarding your enquiry, yes the motherboard can be transferred to a standard case.
With regards to your product’s warranty, please note the customer is able to add hardware on the unit.
Acer would not support any additional hardware added by you nor support any compatibility issues/software conflicts arising from this configuration.
Please contact a local technician while adding hardware to the product.
We would like to inform you, as per our records the unit is out of warranty.
I have written back and asked for confirmation regarding the PSU.
But ......looking at your pictures and the sizes you have given me - your PSU, in my opinion, is non-standard.
I suggest you wait a day or two for official confirmation - but it looks like you will need to go for a new case.
Let me know what you think.