Nice one Yorkshire 89, welcome to the commuter fold!
For the record I do 25 miles each way, 50/50 on/off road, fairly hilly. At least once a week, but try for twice, but need to keep a bit in reserve for weekend riding/triathlons etc. We have secure bike parking and showers too, which is great.
As before, get everything ready the night before, and don’t be swayed by weather forecast, it’s often wrong. I actually revel in the sense of achievement when the weather is foul 🙂
I’m home based so have to carry everything with me including laptop, papers, clothes, shoes, toiletries etc. I use a road/cross bike with panniers and full mudguards.
My missis works in the same office occasionally, she walks to the local station and takes the train. We set off about the same time, I get there about 20 mins before her :-). Similar result if she takes the car as there is no parking at the office.