My advice is to invest in purchasing the whole ensemble after all it won't go out of fashion: it is beyond fashion. So what you need is a black Morning Coat that fits neatly with the tails hanging to just above the back of the knee, a buff waistcoat, single or double-breasted making sure that there is no gap between waistcoat and waistband of the trousers.
My mantra has always been that Formal Dress is not Fancy Dress so avoid garish waistcoats. The trousers should be dark grey/black striped which taper to a narrow bottom breaking once only onto black Oxford shoes (Polished). White cut-away collars with double cuffs look best but if you really want to make a sartorial statement then a separate stiff collar is perfect worn with a silver/grey woven silk tie.
A top hat is mandatory just make sure it fits and carry a well furled black umbrella because the odds are 25/1 that it will rain. Only a couple of furlongs away you will have the opportunity to wear the whole outfit again over the Summer Season and I'm betting that there are bound to be a couple of Weddings to attend, so your purchase will have been a good investment.
All formalwear is available in our stores. For your nearest store click here