You haven't bothered to tell us which direction he was travelling in, but either way he is wrong. The 30mph terminal signs are when you come off of the A421 onto Woburn Rd and the limit carries on its entire duration. If travelling from the other direction, he would have been coming from a road with a 30mph restriction, onto another road with the same. A lack of information telling him it was now 40mph would indicate it was still a 30.
Repeaters are not required at all, the limit is denoted by street lights. If it had of been a 40mph limit the road would need repeaters showing this.
He needs to return the NIP naming himself as driver if he hasn't done so already. For that speed he should be offered a speed awareness course if he hasn't completed one in the previous 3 years, or a COFP for 3pts & £100.
