May I wish you a warm welcome to the CameraLabs forum.
£350 might be a bit optimistic unless the lens is mint. I'd suggest hanging onto it as, so long as you intend to stick with Sony, it could see service on several bodies over the years. Premium glass tends to have a much longer useful life than camera bodies.
As, it would seem, the 16-80mm f3.5-4.5 is going to be out of budget for some time then, assuming you want a general purpose walkaround lens, would the Sony 18-55mm f/3.5-5.6 SAM DT (review
) be of interest and in budget? It could tide you over until you can afford more premium glass and, when in a few years time you decide to upgrade the camera body, it might improve the chances of selling the A700.
But I'd better confess that I've no experience with any of the Sony/Minolta kit so before I dig a hole for myself I'll hand over to forum members who know more...
P.S. Please don't get suckered into any discussions about selling your lens here on the forum. Against the rules, I'm afraid.