I take it that you can get espresso grind coffee from Whittard?
I’m sure you can, as can you in any supermarket.
If you want something special to try for your first drink in your machine, go out and get yourself a can of Illy. (somebody will tell me it’s shite of course.) You’ll find at around £6 a can, you won’t be buying too much of it though.
If that’s a bit saucy on the price front, then a bag of Lavazza will do nicely.
Once you’ve found something you like, you’ll probably want to invest in a burr grinder and buy beans in small quantities to grind as you make your coffee. I eventually did this (with the help of a, ahem, cheap grinder, from above mate).
Like all things in life, feel free to disappear as far as you want up your own bum. 😀