Grade and value

I was hoping for a bit of help from the folks on here. I have had a look at pricecharting and eBay sold and can't find a copy in this kind of shape or on MCS.

As you can see the cover is pretty beat up with colour breaking tics and creases and a scuff on the T of Titans.

I am after a guesstimate of grading and an idea of FMV. It's not going to pay for the yacht but hopefully it's worth more than the £1 I paid in the early '80s.