In reply to iain_cbr:
> I don't do huge expeditions, just a bit of bouldering or maybe a day out on the crag.
I would start looking for something made out of merino wool in a sale. You might need to go to 25 or 30 quid, but I've seen plenty for that price (Cotswold were selling Smartwool ones off at that price and I bought a Decathlon one for 20 which is great).
The main reason is that for what you want any decent baselayer will work just fine, but buy a merino one and if you are sitting in a pub or cafe at the end of the day you won't be thinking "oh god - I stink. How disgusting..." which seems the almost universal experience of wearing synthetic base layers.