can you wear thermal baselayers under your under-suit or will the baselayer not make the under-suit not work as it  should? i hope you can understand what i'am on about

I'd have thought if you wear a good wicking breathable thermal baselayer it'll just act as another layer and complement the under-suit nicely. Not tried it myself though tbh.

Of course! I'd strongly avoid anything that contains cotton, as it absorbs water, feels cold and clingy when wet & doesn't dry out.

My recommendation for UK caving is a Polypropylene (PP) based thermal, such as the Helly Hansen Lifa stripe 'Stay Dry' range (~?20-25 for a top). Check Amazon / eBay for cheap sellers. You want your thermals to be a close fit, practically a second skin with no room for the 'bellows' effect.

Merino wool based ones are warmer, but they're probably too warm for summer caving in the UK, dry very slowly, and are heavy when wet (though supposedly, still warm when wet, but that sounds like rubbish to me... I'd say more just 'less cold' than equivalent cotton! PP tops literally dry off your body). Though if you're dry caving somewhere it's cold, they're ace. They're also exceptionally comfortable for winter mountaineering, biking in the cold and lazing round chilly caving huts. They also don't stink, whereas once you sweat a bit in a PP top, it will never quite smell 'right' no matter how much you launder.

Tops are far more important than long johns, I usually go to wearing 2x tops (often a short-sleave one, and a long sleave one) before wearing a long john.

A good budget option is the 'HEATTECH' stuff from Uniqlo if you have a store near you. These are often 2-for-the-price-of-1, and though not as nice as a HH top, if you find the design without cotton (again, check the label), they're ace. The turtle neck designs are particularly toasty, but a rather strange fashion statement when you're not underground!

jarvist said:

I'd strongly avoid anything that contains cotton, as it absorbs water, feels cold and clingy when wet & doesn't dry out.

...whereas once you sweat a bit in a PP top, it will never quite smell 'right' no matter how much you launder.

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What's the saying about these fabrics?

'Plastic smells, but cotton kills.'

ive seen some on sale in go outdoors there hi-gear (?4.99) are they any good?

I've always used Patagonia Capilene for general cold-weather, mountain biking, etc. It's very good stuff but not cheap and after a while can get a bit whiffy in the armpit area.

I think next time I'll try some merino - I'd love to try some Howies Merino but it's silly expensive and though Howies stuff is lovely, I suspect you pay a large premium for the label.

I always use a base layer under my furry,and even my wet suit.I use a howes  fine gauge Merino wool base layer for cold trips,and an army surplus cool max base layer for summer. it realy makes a differance.

woollydigger said:

ive seen some on sale in go outdoors there hi-gear (?4.99) are they any good?

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If it's these ones: http://www.gooutdoors.co.uk/base-layer-long-john-p163121

They're cotton, so I wouldn't recommend it. My very first thermals were just like that, now they live in my cupboard & are only ever used as PJs on cold nights!

I'd give the Howies merino shirt another nod.

Also, worth checking http://www.on-one.co.uk/c/q/clothing out. If you can face signing up to the newsletter and aren't in a rush, you'll get them cheaper.

i very rarely use an undersuit as i get too hot. instead i wear salopette trousers and a thin baselayer normally, with a jumper if its a slow trip. the baselayer i like is a berghaus extrem tech argentium which i got off ebay for under a fiver. it dries nice and quickly

if you really get cold underground, try thermal rash vest/shorts too, it works for some people