More of a what would you do I suppose.
We've just had some work done in our house. The original quote for the work listed a total price for the job. Underneath the price, written in red, it says, "subject to VAT at the standard rate."
The company doing the work sent the final bill to us last week. I checked this, and the figures did not add up. We'd agreed something else to be added into the work but even allowing for that the figure was still off what I was expecting. I wrote to them querying whether the invoice was correct. They have written back to me saying that I was right that the invoice was wrong on the figures provided, but they ADDITIONALLY realised that they hadn't added the VAT. They've now sent a bill for the whole lot.
I think their originally quote was at best poorly drafted as it is ambiguous whether the original figure was inclusive of VAT. Not sure if I have any recourse. There is nothing in their quote or the T&Cs attached to say whether the subject to VAT was included or not. Feel a bit irritated that I even queried it in the first place but do feel like I've been mugged off!