Sure you will. Those jeans will just be a whole lot more expensive to buy because of customs/import fees.
Likewise, anything produced in the UK will be more expensive to buy for anyone outside the UK, so to remain competitive on a global market UK companies will have to reduce the price of their products, which means they'll have to reduce expenses to not go bankrupt, which essentially means your wages will be lower, and anything you buy that's not from the UK will, as I said, be more expensive.
So to summarize: You'll earn less money and almost everything you buy (because the UK doesn't produce even close to what it consumes, hence, imports) will be more expensive.