John your about 20 years too late ... After the MadChester uprising in the 90's Afflecks went more retro/vintage .... if you want goth stuff you really should have been there in the late 80's early 90's ...
Your best bet is the fancy dress shop on the top floor .. they do hire clothing ... Soho on the second floor do do some good stuff, as does the shop on the first floor (sorry i cant remember their name but you get there by going in the arcade entrance next to CyberDog, up the stairs, when you get to the first floor you turn left, through the door, then immediately right, the shop in question is there in front of you

) .. You also have to understand that what you see at WGW will be their "Sunday best" and affleck will sell more everyday stuff (band t-shirts, black jean's etc) they need to make money and as such they will sell what will sell and sell in bucketloads, not something that will sell once every blue moon but dresses and frock coats are on sale there

.
Afflecks is a good place to pick up accessories, Grin and Extreme Largeness on the ground floor, the above mentioned shop on the first floor (and the shop next to it that sells some really nice jewelry and pocket watches at stupid cheep prices), Soho and Tokyo Royalle on the second floor among others .... If you want to get full blown mourning dresses or the like you may have to look on line (as it has always been the case, Or go down to Camden for a weekend). Attitude Clothing -
http://www.attitudeclothing.co.uk/, Heavy red -
http://heavyred.com/, Plastic Wrap -
http://www.plastikwrap.com/ (more the industrial/cyber goth look but may give ideas) are good places to look for really good OTT goth look. But you would be doing yourself a favour if you kept your eye on the likes of Gothic Beauty Magazine -
http://www.gothicbeauty.com/, Auxilliary Magazine -
http://auxiliarymagazine.com/ (And free to download the pdf

), Devolution -
http://www.devolutionmagazine.co.uk/ (New webbie coming soon so bear with them) or Alt Fashion -
http://www.altfashion.co.uk/ .. All of these cover the culture, music etc (some like Devo and Aux also cover the likes of models, photographers and make up artists, Aux will have a section in each issue that covers a "Style" to give you an idea to make up one set dress type of thing, it also covers make up ideas from time to time) alt fashion can seem a little Scene/Emo at times (the type of guys you see hanging out round the back of Urbis in Manchester as opposed to "True" goths LOL) but give it a look.
Recent years the goth/industrial scene has migrated eastwards with more gothy stuff over the border in the wilds of Yorkshire (as well as most of the bands going to play that side of the Pennines

) this side went more Brit Pop, Rave and rock and the goth scene sorta died over here

there are a few shops around .. Crimson Kasket in Conway, There is a shop (or was) in Ashburner street market in Bolton, there is supposed to be a good one in Preston (I will ask Kat to see if she can find out its name and get back to you), Not sure about the likes of Liverpool but I know Chester has a branch of SoHo's, the same as Afflecks. I shall keep a look out for you ... Oh and dont over look smaller shops .. Morgana Clothing in Wakefield -
http://www.morganadesigns.co.uk/General/News.html will do custom, made to measure, waist coats and some really nice stuff .. I was thinking of getting one to go with the long black coat I have but never got round to it.
If you would like to borrow an issue or 2 of Devo, Unscene (More music than fashion), Alt Fashion or Gothic Beauty let me know and I will bring some issues in for you to borrow for a mooch .. but really take a look around .. Aux site will have links to fashion houses (Like HeavyRed) as will Gothic Beauty, mooch round Attitude and you will see brand names .. if you punch the names into Google then you will end up on other sites with other "houses" you have not seen and your adventure will go on.
Oh and as your post was on a Sunday I assume you went that morning, if so you will only find the ground floor open on a Sunday .. you should go on a saturday the whole place is open .. I could meet you and give you a guided if you should see fit
