HV/LV - How to demonstrate UK electrical design competency with foreign resource?

Hi

Can anyone help me understand how to define competent in electrical design for an installation in the UK by an international resource.

We are a UK technology developer and have recently engaged with a foreign design firm for the electrical design on a UK installation. Although these guys are very experienced I don't think I can call them competent in UK electrical design if they don't have experience in British Standards, UK electrical design work or any relevant BS qualifications. Is that a reasonable assumption ?

I am interested to understand how others have overcome this 'competent' stamp ? through third party verification from UK competent person, training courses and use of software packages such as Amtech or all together? although academic qualifications don't demonstrate relevant experience in the UK.

Thoughts and experiences would be very helpful.

Kind regards

Chris