US Tax Resident/UK Citizen making GBP investments in UK?

Hi

I'm a UK citizen living in the US (Chicago) on a L1 Visa so am US tax resident. I'm on a 3 year work assignment with a housing allowance paid in dollars, but I'm still getting paid in the UK in pounds.

My wife (we married in the UK years before moving here) is a US citizen so it would be relatively straightforward to remain permanently if we decide, but for family reasons it's looking increasing likely that we want to return to the UK at the end of the assignment.

We're fortunate that I can save the majority of the UK paycheque and it's just sitting in a very low interest savings account so I'd like to make some investments (nothing exotic, a low cost tracker). I know I can’t open an ISA as I'm not UK tax resident but I thought that I could maybe open a UK investment account and hold in there but I'm hitting a complete brick wall as it seems no-one will take US tax residents.

Does anyone have any experience of doing this or are the IRS such a PITA they’d rather turn away the business than deal with me?

(I'm aware that you'd need to be careful with the exact investments you made to avoid heavy US taxes, but I'll worry about that if and when anyone will take my money!)