Hi,
The guidance below states "If you have a temporary presence of human and technical resources in the UK, this does not create a fixed establishment in the UK":
Place of belonging
Section 6 of the guidance above gives the place of supply rules, and yes, you should check whether the reverse charge is applicable to the supply you are making. The conditions when the reverse charge is applicable are detailed in section 5 of the above guidance.
Please note that where the customer accounts for the VAT using the reverse charge, these supplies do not count as your taxable supplies in the UK. If you determine the reverse charge is not applicable then please refer to sections 9-13 in the following guidance, as these give guidance regarding a non established taxable person and VAT registration:
Non-established taxable persons — basic information
Thank you.