There is information on offshore investment bonds here.
You made a final gain of £152,918 on the surrender of the offshore Friends Provident policy. Assuming both you and your wife were the joint beneficial owners, you each have a gain of £76,459. As this was an offshore policy, no basic rate tax has been treated as paid.
As the gain accrued over 12 or 15 years, you are entitled to top-slicing relief which is based on the number of complete years the policy ran for (12 or 15) so as to limit any 40% tax liability which is due to a one off event. You should contact Friends Provident to find out whether you should use 12 or 15 years for top-slicing relief purposes. I would say 12 as that is what you said was on the certificate.
If the gain for each of you is divided by 12, the top-slice is £6,372. Tax at 20% on that is £1,274.40. Multiply that by 12 and your maximum tax liability is £15,292.80.
If the gain for each of you is divided by 15, the top-slice is £5,097. Tax at 20% on that is £1,019.40. Multiply that by 15 and your maximum tax liability is £15,291.
Either way it makes little difference to the tax liability. If you have unused personal allowances, these can be offset against the sum of your regular income and the chargeable event gain which is £76,459 for each of you and should reduce the tax liability.
The life company will report the gain to HMRC. You and your wife, however, still need to report your respective gains. After the end of the tax year, you should contact the tax office on the number here and ask if you and your wife will need to register for self-assessment or whether HMRC can assess the tax you will need to pay outside of the self-assessment system.
I hope this help but let me know if you have any further questions.