lavatory faucet change out

[pjude]

My current faucet is leaking and the finish is coming off so I want to replace with a house faucet...problem is in the change-out. I have 2 rigid copper supply line attached to the gray plastic supply lines. there is no room to raise the faucet up after taking the hold down bolts off. Is it best to cut the copper lines and attach another fitting or is it best to cut the gray plastic.Or is there another method?Pete