Thanks all for the ideas - and the understanding.
Good idea about a last few happy pill-free days, Juliet, but unfortunately they won't be happy and she won't be playing if she doesn't get any pain relief (and more than just the easy-to-administer Metacam.)
Anyways, I got some cocodamol down her twice today, the morning one hidden inside one of a series of "whole smelly dried small fish" treats (given alongside Jilly getting the same, so Dot would be in danger of losing any treat she dropped, making her slightly less discerning) and the second in one of four pieces of freshly-roasted fantastic organic happy Hampshire pig sausages scattered on top of her favourite dinner (pieces of roast chicken and skin.) She did actually detect it the first time she picked up that piece of sausage, and spat that piece on the floor, but I retrieved and rewrapped it and snuck it back in her bowl, and it went straight down the second time. (*)
The tramadol hidden in another "whole smelly dried small fish" treat was detected before the treat was even in her mouth, despite being totally encased within the fish's gullet, so it must have a very pungent smell to her, and it clearly tastes awful. She wouldn't even eat the section of the fish where the tablet had been after I removed it, even with Jilly hovering nearby. So I put on my big girl pants and managed to put the tablet right on the back of her tongue (first time I have ever managed that with this dog) and got it down her.
She was still limping but happier and running, wanting to play with Jilly, on the afternoon walk, so it is clear that the pain meds cocktail will work, for a while at least.
I have a variety of things to use as treats on her feed to hide the cocodamol in, so I am hopeful that I will be able to get those down her without too much bother henceforth.
I have ordered some "pill pockets" to try, which will be there by Weds. The pill gets completely encased in a tasty treat, apparently. I have my doubts even they will work with the tramadol, so I also bought a pill gun. I figure pill gun, do it quick, then a piece of sausage (unmedicated); hopefully she will accept the indignity of being coerced to take the terrible pill in the light of the yummy sausage which follows it.
And I will call the vet to see if there are any other ways the tramadol could be presented - a liquid to mix in a strong chicken gravy (her favourite gravy) served with half a tin of Chappie might just work.