They fit perfectly--def not tight. I hate tight jeans. Furthermore the stretch makes them so comfortable you aren't aware of them.

Sounds like you've found a solution, at least for the short term. Carradice would be another option, but how about a big expandable trunk? I think BF'er Jim from Boston uses one of these: https://www.amazon.com/Inertia-Design.../dp/B000QG1ESU

Honestly I wear my work clothes while commuting. Thing is I am not trying to race to work, but rather go at a nice slow 10-15 kph. I also have just over a 7km commute so it's not that bad even in high heat and humidity.

I use an Arkel Commuter bag on a rear rack to carry my clothes (business casual pants/shirt/socks/underwear/belt in a grocery plastic bag; I keep shoes at the office.) Also pack a towel/soap & shower sandals. Occasionally I will also transport my laptop, as this Arkel bag has a nice suspended padded sleeve in it for the laptop. I can alos fit a small rain jacket & pack a lunch, but it's a pretty tight fit with all of that
My commute is 16 mi each way, and I try to keep a good pace of about 17-18mph as I consider this my daily exercise, so I wear cycling clothes & shower/change at a nearby gym.
I've been wanting to try the eagle creek pack-it folder though as it seems it would do a good job of keeping the wrinkles away

I always preferred to stock up food and clothes using my car on non bike days or the weekends

Panniers are my primary cargo device. I don't like riding with a backpack at all. I can usually fit a change of clothes and a small lunch into one small bag. You do need to have the correct type of rear rack to hold them.

A trunk bag, or even a basket can also work well. With a basket, you'll want some sort of bungee or net to keep stuff from flying out.

Wallingford bike parts (www.wallbike.com) carries all the Carradice bags. Peter White cycles does as well. I have a barley and find it to be just a little small. If I were to buy another it would be the Pendle.

Iron & board at work.

I take a clean shirt and singlet in every monday - they last all week.
Trousers last a couple months.
I shower each day and work in aircon and don't get sweaty.

Usually I wear my work clothes for my short 6 mile commute in the morning. In the heat, I'll wear a t-shirt and change it out when I get there. I use a timbuk2 XL messenger bag most days -- but I have front and rear racks and panniers if I feel like it. I prefer the huge bag because I can hop off and everything I need is already attached to me. Yes, it causes more sweat than panniers.

Thanks - excellent advice. So despite my desire for a SINGLE bag solution I could not really find anything that would seem to do the job, so I shall continue with two bags. However I shall move to a Carradice Nelson Long Flap for the saddle bag mounted on a Bagman Quick Release with Expedition Support. https://www.carradice.co.uk/index.php...&product_id=37 and https://www.carradice.co.uk/products/other/bagman. As I ride a small-wheel bike this gives enough room underneath for the Arkel Tailrider. The quick release will allow me to take off the saddle bag quickly, and the Nelson is a bit larger than the Glenbrook, it also seem to have larger outside pockets. And I think I'll reverse the current procedure in that the Arkel will hold the permanent gear and the Nelson will carry daily clothes, lunch and whatnot. The Arkel will stay mostly in place on the bike and not be removed every time I get home, now it will be the Nelson that I remove and carry with me.

I road with a backpack for some months and I really did not like it, although it was the best organized solution, with room for a laptop or iPad, lunch, clothes and everything neatly organized. I guess if I had a shorter commute I might have got used to it, but I found 14 miles on a hot day to be very uncomfortable. I like also having the weight lower down.

North Road Bicycle Imports had the Carradice stuff https://northroadbicycle.com/ and I hope it will arrive this week.

I do so very much enjoy buying stuff for my bike - two bikes as of a month or so ago, I enjoy it so much I bought a second bike so I can buy everything twice... I am glad my wife does not read this forum!

Sigh.

Thanks everyone.