My scrappy says the price is starting to shoot up since brexit given the pounds falling value against the dollar
Your scrappy is correct.
The price of new copper has risen anyway, even in dollar terms, from a recent low of about $4600/tonne to about $4913/tonne at close of the markets tonight. That rise of just under 7% is not remarkable - the market often swings by that amount, and as recently as March 16 and May 16, the dollar price occasionally went over $5000/tonne.
However, if you factor in the approx devaluation of the pound against the dollar, post Brexit, then you have another 8% to 10% increase in the sterling price, as you need more sterling to buy a dollars worth of copper. Put the two together, and you are in the high teens in terms of a % price change.
Although the correlation is far from exact in the short term, in the long term the scrap price will shadow the price of newly mined, raw copper. Scrap can never rise above the price of new, otherwise the mining and smelting companies would simply take their virgin production straight to the scrappie, which is clearly nonsense.
So expect a better price at the scrappie. The downside, of course, if that you should also expect a higher price at the merchant. You can't have it both ways!