You propose a possibly-difficult course.
If you are not already an established Ebayer, there will be trepidation on the part of buyers. This may be allayed with the quality of your auction copy and your images; you must provide clear and accurate images to achieve the best results. Shipping cost is also a consideration as you're in Great Britain and the vast majority of your audience will be across the pond. They will be factoring the cost of shipping into their bidding.
Another thought concerns
VAM variety. Oddly enough, all but the most popular VAMs sell for higher prices when sold unattributed; buyers wish to believe they're getting a "cherrypick." Worse, a Morgan variety collector who's on his game will check your other auctions, and if you're offering attributed Morgans as well as unattributed ones, they'll know you've researched all your coins and your unattributed offerings are likely not of value to them. So one must take the balance of the evidence when choosing whether or not to attribute.
With that said, by all means find out for yourself whether any of your holdings are of added value due to variety. Amongst P-Mint Morgans, very few dates besides 1878 and 1921 have added-value varieties.
Here's an example, one of my auctions which ended last night:
http://cgi.ebay.com/ws/eBayISAPI.dl...TRK:MESOX:IT That was a very popular added-value variety, and I'm a longtime
ebay seller with a known specialty in
Morgan dollar varieties. It did pretty well against the known market. You'll have to come close to my images if you're going to maximize your value; buyers will need to be able to grade from your pics if you wish them to bid appropriately for grade.
Which allows me to segue into grading. Given the inherent cost - not to mention time involved - of sending coins to the US for grading, I should think you'd want an arbitrary value cutoff of, say, US$250 to warrant the effort of having the coin graded. I would use ANACS (accuracy & cost-effectiveness) or PCGS (highest market value but more expensive) as your grader.
If you're going to
ebay, maximize your chances across the board. Write a clear and concise auction. Include images of grading quality. Cause the auction to end on a weekend evening (I usually end mine Sunday night, but Fri/Sat are equally fit) at no later than 2300EST, allowing bidders from both coasts to be at your auction during their free time.
Or, consider contacting Bobby and Susan, the owners of CCF, regarding their consignment service.

They've already developed the
ebay clientele for your coins over many years and thousands of Feedbacks.