Well, it's too new to be on Google Street View, but looking at the PCNs there seems to be only one restriction sign, which could be considered inadequate under the duty in Regulation 18 of The Local Authorities’ Traffic Orders (Procedure) (England and Wales) Regulations 1996
https://www.legislation.gov.uk/uksi/1996/2489/regulation/18Other thing to consider is, is there advance warning of the restriction ? And indeed yes, there is at the turn into Crystal Glen off Heathwood Road. In addition this GSV view is dated July 2023, so the restriction has been there for some time now.
https://maps.app.goo.gl/zTTV5UVykPoYViFa9At the other end, the previous signs are shown on GSV, which are the usual FLying Motorbike signs, but which allow access. Clearly these failed to prevent rat-running, so have now been replaced by the signs at the other end.
For representations, I would submit representations on the basis that the person who drove your car was helping out for a funeral and was totally unfamiliar with the restrictions, and the delivery of all three PCNs on the same day means you were totally unaware of the contraventions. Point out that three PCNs seems a disproportionate penalty for a simple error and request that they accept payment for the first PCN and cancel the other two.