M&S have a roast - special (the £15 deal I think) on at the moment...you could try passing it off as your own hard work using your own roasting tins!!
Just don't do what I did last night for supper, faffed around at work got home late, so was just starting to peel pots when friends arrived, was trying to keep it simple with bangers and mash and onion gravy...
Finally, sat down to eat and realised I'd forgotten to cook any other veg...I had spring greens in mind but was so busy chatting and drinking wine I forgot!
If you can get the large Aunt Bessies Yorkshires, then I'd agree a nice beef casserole in lashings of gravy would be easy to do, looks great when you ladle it all in to the puds and serve up with some veggies and roast taties - you could get it all readytonight, and pop the casserole in the oven cooking first thing which makes it easier when you're still trying to fly round with the hoover tomorrow!
Nice beef stew, with roast pots brussels.
Beef stew( stewing steack and 1 onoin chopped, 1garlic same, brown, put in casserole, with 1/2 pint beef stock (cube)1/4 pint red wine, mushrooms quartered, carrots slicced, pinch of Tarragon and couple of Bay leaves. 15 minutes before end thicken with Bisto gravy powder(original) pour in slowly so it doesn't get lumpy,keep stirring, 180 c not sure on gas about 1-1 1/2hours and I cook the roast pots for about an hour bottom shelf