Where to source cabinet grade plywood?

[urbanstarship]

I'm planning to build a painted cabinet around my washing machines to tidy that part of the house, but I'm a bit overwhelmed with how to source the sheet materials for the project. Birch plywood prices are a bit insane, but I don't know if going to cheaper hardwood plywood or MDFs will be good enough quality. I live in Somerset with a mid-sized 4-door car. Any ideas?