This seems to be one of those debates where the people on each side already have a fixed view on issues of this type, and are not going to be persuaded by the arguments of the other side. I find myself leaning toward supporting Abbey. Many of those who do not have made the point, in one form or another, that
"It's a departure from accepted practice to charge potential customers to look at your products."
The point I wish to make in response is this: 'accepted practice' is a moveable feast in a market which has changed as much as the travel\tourism market. The flights, the hotels, the guided tours etc. are not Abbey's 'products'. Abbey's 'products' are advice, planning and booking of such products, which are sold by third parties. The old business model is that Abbey would get a fat commission from the providers of the products. Internet sales are gradually destroying that model.
These days, Abbey are like a 'personal shopper' or a wedding planner. They help you to find a product which is right for you.
It seems that Abbey get a lot of window shopper\tire kicker prospects in the door. This might be simply due to having a location with a lot of footfall. Alternatively, it might be because Abbey have a strong reputation (I really have no idea - I don't do much foreign travel).
Abbey want to change the mix coming through their door more toward committed purchasers\strong prospects, or at least that is the logic implicit in their up front charge.
I would not be at all surpised to see more travel agents moving all the way to a fee based model in the future. Time will tell.