Here is a definitive list of what is required to charge VAT:
What a VAT invoice must show
A VAT invoice must show:
an invoice number which is unique and follows on from the number of the previous invoice - if you spoil or cancel a serially numbered invoice, you must keep it to show to a VAT officer at your next VAT inspection
the seller's name or trading name, and address
the seller's VAT registration number
the invoice date
the time of supply (also known as tax point) if this is different from the invoice date - see below
the customer's name or trading name, and address
a description sufficient to identify the goods or services supplied to the customer
For each different type of item listed on the invoice, you must show:
the unit price or rate, excluding VAT
the quantity of goods or the extent of the services
the rate of VAT that applies to what's being sold
the total amount payable, excluding VAT
the rate of any cash discount
the total amount of VAT charged
The Getty letter I have seen does not mention what rate of VAT applies, a VAT registration number or a sequential invoice number. They also don't mention the VAT for each item, just a total VAT with no VAT rate.
The letter is a couple of years old now so not sure if their practice has changed but if their letters are still unchanged I think we can see why no cases go to court here in the UK.