I don't think you need to go mad with the toiletries, you can get liquid soap in small plastic bottles. Then there's the toothbrush/toothpaste stuff- cut the weight by taking an almost finished tube...maybe a comb....?
One strategy might be to sit next to somebody who smells even worse than you do and blame them...
As far as tops/baselayers - you can get merino wool baselayers which are expensive unless you get them at Aldi, but they don't get niffy. (£40 in Cotswold, £6 in Aldi! - with the same manufacturer's labels on them too)) Walking tops from outdoor shops tend to be variations on polyester. You can also get very light micro fleeces which are useful. If you're on a budget, gelert stuff is reasonably priced and is OK - otherwise you pay for the name. Some of the "skiing" stuff in Aldi is also quite good and pretty cheap and , I guess would be fine.
For trousers, you could use another pair of jogging pants, or a pair of ronhill running pants. These dry very quickly and are light, although if you buy the tight versions, you might attract the wrong kind of attention in the more effete Southern pubs, or you'll look like Max Wall. You certainly won't need to use the rolled-up sock to emphasise ...er....stuff.... Get somethin baggier!
