@Olive1989, I would think that a UK account with IB should allow you to buy US equities or ETF's, I don't see the issue. As always you'd be having to deal with the FX as well as trade & account maintenance fees & per trade cost
Have you called them to clarify that you want to buy/trade US equities?
As suggested above a Vanguard, Blackrock may be another alternative.
Did a quick look around to see any alternatives.
As a low cost alternative comparison easy to use, execute trades UK brokerage, check out
https://media-prod.ii.co.uk/s3fs-public/pdfs/rates_and_charges_uk.pdf
in the following, also use the sidebar to get the information
https://www.ii.co.uk/etfs?utm_source=Homepage&utm_medium=Homepagehubbox&utm_campaign=ETFsHub