If your boundary is still being built or altered, give Wesslink the planned sequence. A wall, gate opening and fence may be completed at different times. Identify which sections are finished, which are temporary and which still depend on another contractor. The assessment needs to relate to the intended completed installation, with any unfinished work or inaccessible section clearly recorded.
Build a simple timeline from documents you have: property handover, fence installation, later alteration and current inspection request. Approximate dates can be labelled as such. Keep the installation records with the property file so a later buyer or occupier can distinguish original works from additions. Where several parties were involved, ask each for the documents covering their work instead of assuming the housing provider retains everything.