If you aren’t sure if you are a "competent person" don’t worry! It’s a good sign that you are asking questions - it shows that you are taking the topic seriously.
You - or someone on your team - likely meets the definition of a compentent person. Natural England has said (opens in a new window) that, for small sites, a competent person may be "project managers and architects". The British Standards Institute also says (opens in a new window) that landscape architects are another example.
As you are using the Small Site Metric (SSM), the definition of competent is based on the BS 8683:2021 definition: "[a] person who can demonstrate they have acquired through training, qualifications or experience, or a combination of these, the knowledge and skills enabling that person to perform a specified task". Remember: you only need to be able to meet one of the three categories.
Experience. Do you or someone on your team have any experience with landscaping or dealing with habitats, e.g., in architecture (especially softscaping), or project managing a development?
Training. Have you, or someone on your team, had training (e.g. on undertaking BNG or habitat identification?) If not, there are several courses that you might want someone on your team to take (these should only take a few hours, there may be a cost):
CIEEM Training Courses: offers a range of online training courses for BNG Practitioners aligned with the CIEEM Competency Framework.
UK Habitat Classification Training: offers a range of online and field-based training courses on the UK Habitat Classification and related subjects such as Biodiversity Net Gain.
Qualifications. Do you or someone on your team have any relevant qualifications that would qualify them as an "ecologist"?