Go into any half decent ‘Adventure’ shop (Cotswold, for instance) or even one of the running shops that now seem to be springing up on every corner and look through their offerings. Then try something as simple as M&S or Primark or TKMax to see what they might have.
The need / desire to wick away sweat, is not unique to motorcycling, though the reasons for the sweat being generated differ between the healthy hiker hitting the hills and Big Bob on his bike in the sun; the solutions are all (near enough) the same.
From there it’s near enough down to taste, style, colours, cost and practicability. Do you want natural wool and risk the moths turning your expensive t-shirt into a string vest? Do you want bright colours or dull greys? Do you mind seams or do you think they’ll chaff your nuts? Do you want crew, roll-neck, v-shaped, zippped or unzipped, t-shirt or long sleeve? The choice is all yours.
The need / desire to wick away sweat, is not unique to motorcycling, though the reasons for the sweat being generated differ between the healthy hiker hitting the hills and Big Bob on his bike in the sun; the solutions are all (near enough) the same.
From there it’s near enough down to taste, style, colours, cost and practicability. Do you want natural wool and risk the moths turning your expensive t-shirt into a string vest? Do you want bright colours or dull greys? Do you mind seams or do you think they’ll chaff your nuts? Do you want crew, roll-neck, v-shaped, zippped or unzipped, t-shirt or long sleeve? The choice is all yours.
I've had a good few opportunities to put it to the test and it works very well. Very comfortable on as its seamless, nice and stretchy too whilst not being as tight as say a compression top. The thin layer it provides under your kit prevents that sticky sensation you get on your arms when you wear a t-shirt under your gear. The wicking effect works well too - when you take the top off after a warm spin, even though it feels damp to the touch, your skin is dry. And the odour management is top notch - even after a long days spin in the heat the gear was pretty fresh. For me that would most certainly not be the case with a normal cotton t-shirt or even a 'technical' type of top. 
