Mine was over 8 miles so I did the leggings and t-shirt & change thing. If you roll things up in a pannier they dont' come out too badly, but this is coming from a complete ironing slattern so your standards may be different! Kept a flannel and deodorant in the office along with a pair of smart shoes, and never had any complaints.
Would suggest a decent breathable coat for the winter to keep out wind and rain, and a good pair or gloves (high viz for preference) but you'll soon warm up after a mile or so on even the coldest morning.
Everyone cycles to work around here, and if your commute is less that 8 miles each way people generally wear their work clothes.
My cycle ride is just over 4 miles each way, and I just wear my work clothes, no point wearing different clothes for such a short cycle, especially as you're not on a road bike racing and breaking out in a sweat!
Wear the high vis jacket though, and get some high vis trouser clips too, for when you wear trousers.
Leggings are great, as are tights and skirts, I avoid wearing loose trousers as I don't like wearing ankle clips.
Am going to be cycling about 4 miles each way to a new job. Bike is an old fashioned step through one complete with wicker basket, I'm just wondering what is the best thing to wear I'm thinking leggings, long sleeved t shirt, trainers and my hi-vis jacket, but any tips and hints? I'm also trying to work out how to get my clothes there without them being too creased. Apparently there are showers at changing in the new office, but I'll find out