I find the company website very confusing. I cannot tell if the company or its owners are in the UK or US or the tax experience/qualifications of the owners.
They may be great guys, but I simply can't tell if they will give you best advice when it comes to the interaction with UK type issues such as our weird tax year, penson plans, ISAs and the UK/US tax treaty.
I normally recommend a dual qualified US/UK adviser.
I have never come across this firm previously in well over 20 years in the US/UK tax industry.