I'm not sure on the pp but I've been a few times an have the grilled chicken breast with jacket potato and piri piri sauce. Lowest thing on the menu! And then obv fill up on the freebie salad with the low vinagerette dressing. Luckily the menu has the calorie content of everything!!!
Also, check out my fitness pal as you can search lots of meals and then use the info on there to calculate the pp!
Hope this helps! Enjoy!!