It’s hard enough getting everyday clothing thats going to fit you if your overweight but trying to get cycling clothing in the largest sizes possible is fraught with difficulties.
Your going to need a set of cycling shorts with padding and for a bloke he should be looking for a pair of bibshorts. The reason for getting bibshorts is they are not going to roll down over your gut or catch on the nose of your seat when you go from a standing to a seated position. Either way it’s not a situation you want to get into.
If youve got a problem with body image wear tracksuit bottoms over them, they keep you a bit warmer in winter too. Sizing between different manufactures remains a mystery but they are all on the small size.
To cut to the chase on shorts try Decathlon Sports in Stockport they have a blue tag range thats cheap and go up to XXXXL in some ranges, they have changing facilities too.
Aldi and Lidl have cycling clothing and equipment at various times of times of the year under their weekly offers. I started out with this kit, it well made most of it and very cheap. Just be at the front of the queue when the doors open. If it fits buy two of them, as one of them is going to be in the wash.