Hi Rainy
That looks like a good deal - when we ran figures there (a few months ago) it showed a 1% AVC for a 40 year old male up to age 65 would purchase an estimated pension of 1.6% of salary at retirement (this is with 50% spouse pension, no pension escalation, retirement age 65).
In your example - your are getting a 1.67% GUARANTEE pension (with spouse pension I presume?, with escalation I would imagine in line with state pay increases?, with retirement age 60?) and you are only being asked to contribute about 0.8% of salary - even less cos some of this based on pensionable salary.
Is the retirement age 60?
If so the deal is excellent.