Good - you`re clearly thinking about colour shape, dimension and texture.
Bad - don`t roast the potatoes - boil, put them back on the heat for a few moments, crush them with a fork, add some butter/olive oil, check seasoning. Put the CRUSHED NEW POTATOES slightly off centre, i.e., bring it down toward 6 o`clock. If you don`t understand what I`m trying to say send me another message.
Broiled striploin - to me this is grilled sirloin - remember I`m in the UK. Cut so that you have an uneven number of pieces for each portion, thus 2 cuts will create 3 piecess, 4 cuts will create 5 pieces, and you need an odd number of pieces for the plate to look effective. I wouldn`t do more than 5 pieces per portion, i.e., cut with 4 strokes, at an angle of 45 degrees (not straight down) of a really sharpe knife. Psychologically, the odd number has more visual impact then an even number. If you don`t believe me go and study the windows of your nearest department store.
Very Good - broccoli - don`t overboil. Practise steaming! or practise this - boil until just al dente, place a heat proof sieve or strainer on a pan, strain the veg., return the second pan with the strained boiling water and veg to a low heat. The water must not touch the sieve and must be kept at a gently simmering temperature. Cover with a saucepan lid. This will keep the broccoli warm and prevent it from too much overcooking so long as it`s not left for too long. How about a topping of lightly toasted almond flakes for the broccoli - introduces texture?
Red peppper - I`m thinking colour, flavour, dimension and texture here. I recently posted a recipe for Cauliflower Snagow style on the BBC TV - Lifestyle - FOOD - messageboards -FOOD CHAT. This is blanched red peppers halved lengthways and filled with cauliflower in sauce mornay/cheese sauce. This can be prepared ahead of time, even the day before and reheated in the oven. It would go well with the steak and sauce and saves hob space and last minute things for you to do. All you would need is one half pepper per person with broccoli served either side of the pepper.
Finally a word about the sauce - spoon a thread over the meat and some create, well, like a smiley face - 9 o`clock>6 o`clock>3o`clock and serve any remaining in a pre-warmed sauceboat at the table for guests to add to their plates.
Good luck with the meal - wish I could be there,