Hi Claire B,
If you are providing services to a customer based outside the UK then these sales would be classed as being Outside the Scope Of UK Vat and so would not go towards your turnover when considering the need to register for VAT.
Please see the guidance below;
6. The place of supply rules for services
I would recommend speaking to the software provider regarding how this is accounted for as we can't advise on this.
Thank you.