when my mum died, my sister and i had her 3 stone diamond engagement ring, and her mother's (our grandmother) 2 stone diamond engagement ring, made into two pairs of diamond stud earings, and one singel stone on a fine gold chain.
like you lottie, i never got engaged, didn't see the point at all, just started saving up and got married when we had enough for a deposit on a house. the first christmas after we were married, i was presented with a lovely simple diamond ring, which i wear as an engagement ring next to my wedding ring.
i too have a number of rings just shoved in my jewellery box, inherited from various family members, also the skeletons of the two engagement rings which had the diamonds removed. the older i get, the less sentimental i'm becoming about all this stuff and i feel at some point i'll probably do what you're contemplating lottie, and sell it.
i have a gold 'pipe' necklace and matching slave bangle (i think that's what it's called). those two items, and a load of cheap and cheerful earings and necklaces picked up here, there and everywhere (mainly on holiday) are the only jewellery i like wearing.
sell it lottie, and enjoy doing something nice with the money :o)