UPDATE
I thought I'd add an update as to what's happening. My GP got the swab results back and told me that there was no infection in the wound. He also said that due to the excessive flow of fluid from the wound he thought it best I get advice from my surgeon.
For a week now this fluid which I can only describe as a greasy cup of tea has been flowing steadily and made a hole about the size of a five pence piece at the bottom of my scar.
I contacted the ward who said to go to A&E so off I went again and saw the same surgeon I'd seen last Saturday when it started. He called his senior who had a look and said basically, they stitch together the muscle, and stitch the top skin layer but this leaves a gap in which fluid from inflamation, fluid wash from surgery, fat and general liquid can form and escape from the easiest route.
The surgeon then took a scalpel, and opened the hole up to make it even bigger, you could sit a golf ball in my new second belly button. He didn't use anaesthetic or anything to numb it first, just cut away lol.
The new larger hole is now packed with an alginate (seaweed and silver) based dressing and is being repacked daily by the district nurse.
Whilst it's got worse to get better, I'm at least reassured that the district nurses are taking responsibility for the wound and in time, it should heal. I'm still taking the antibiotics as prevention rather than cure as I would hate the wound to become infected now.
Apart from that, post op I'm feeling quite good and encouraged by my weight loss of 2.5 stone in a month overall. It's been a set back but I'm sure it will sort itself out.
I've never heard of this happening before, but maybe something for pre-oppers to look out for.