As others have said, the entitlement to SSA benefits is unaltered by renouncing, and any benefits are only taxed in the UK.
If you have 40 quarters or more of US minimum contributions, claiming SS benefits is as normal even if you have renounced, but WEP does apply if you are applying on your own account. If you have less than 40 quarters of minimum US contributions, you are still entitled to the SS benefit provided you have sufficient UK NI contributions, but the benefit is based only on the number of US SSA contribution quarters. This is possible by the UK/US Totalisation Agreement and does not effect your UK NI benefit. In the latter case, WEP does not apply.
As was said, I know of at least 5 or 6 UKY members who have renounced. "DrSuper99..."(?) gave a full account. KFDancer may remember the correct user name. Check out the past posts in the members list.
I'm also aware of several who thought of renouncing, but were deterred by the Exit Tax threshold. (All assets, including the full value of retirement plans, home value, investment assets, etc. greater than $2 million.)