In my opinion the absence of a surge protection device (SPD) is classified as a C3 fault in an EICR. There are questions there i.e what protective devices are installed in the CU (RCBO's ,AFDD's ?) and where the property is located , close to open field , rural area etc. Have you performed the testing of circuits installed in that CU including the protecting devices in order to establish any unusual activities like transient overvoltage since the SPD has blown off? In my opinion, either there have been a surge for the spd to blow off or it simply decided to fail. Although this condition is not immediately dangerous, it is strongly recommended for improvement.

The current edition of the IET Wiring Regulations, BS 7671:2018, states that unless a risk assessment is carried out, protection against transient overvoltage shall be provided where the consequence caused by overvoltage could:

• Result in serious injury to, or loss of, human life; or
• Result in interruption of public services and/or damage to cultural heritage; or
• Result in interruption of commercial or industrial activity; or
• Affect a large number of co-located individuals.

states that unless a risk assessment is carried out, protection against transient overvoltage shall be provided

Other way around I think ,. (and I think your list has missed a corrigendum/amendment or two) - where an overvoltage could result in serious injury or loss of human life, or significant financial or data loss then SPDs must be provided - only in other cases may they be omitted (by the owner of the installation declaring the risks are acceptable).

   - Andy.

states that unless a risk assessment is carried out, protection against transient overvoltage shall be provided

Other way around I think ,. (and I think your list has missed a corrigendum/amendment or two) - where an overvoltage could result in serious injury or loss of human life, or significant financial or data loss then SPDs must be provided - only in other cases may they be omitted (by the owner of the installation declaring the risks are acceptable).

   - Andy.