I bought a selection of knickers from sainburys which have been fine. I bought a basic 95p potty from asda and it's been fine. It's easy to wash under the tap (I.e sides aren't too thick) and it fits under my pushchair for when j am Out and about
Cheap pants from ASDA that I could bin if needed. Once dry for a month we went and bought 'special pants'...he chose ones with cars on! Potty- I really like the BabyBjorn potty chair, we also have a smaller BabyBjorn too...we had these from DD as they were the only make available (we were living abroad). I have a 99p one in the back of the car, just in case!