Don't step there!

The only venomous snake in the UK is the adder (http://www.herpetofauna.co.uk/adder.htm) which usually only bites people if actively hunted or harrassed. In terms of plants, stinging nettles are all over the UK and can be painful although not as bad as US poison oak.

We also have Lyme Disease in the UK but not as bad as the USA (my brother and sister in law were infected when camping in CT). So the usual precautions against ticks required. Particular areas where there may be a higher risk include Exmoor The New Forest The South Downs Parts of Wiltshire and Berkshire Thetford Forest The Lake District The Yorkshire moors
The Scottish Highlands

Adders are found lots of places (I saw one in Switzerland) but they are not aggressive. Nettles are painful for a very short time and do not produce a lasting rash like poison ivy. They are very common in the US so you have likely encountered them already anyway. Ticks are the big worry.

(Nettles) ... are very common in the US Stinging Nettles is a weed I had never seen in the USA. Are they now common? They are a completely different plant from common thistles and give a nasty ouch and rash. Immediate treatment with a doc leaf, almost always in the immediate vicinity, will usually remove most symptoms.

Stinging nettle (Urtica dioica) is very common all over the US. Here is a distribution map: http://plants.usda.gov/java/profile?symbol=URDI They tend to grow in disturbed places. Our forest parks are full of them. Oddly enough, they are quite good to eat. (Boiling removes all of the stinging stuff. Pour off the cooking water and rinse once.) They can be eaten like spinach. Some of teh frou-frou Seattle restaurants serve them in the spring when they are young.

Definitely avoid nettle! It looks like a mint plant with fuzzy leaves. It is abundant in England, Wales, and Scotland in the countryside along hiking trails. I very much regretted picking a stem of it-lots of tiny barbs that are tricky to remove.

Gorse has lots of prickles and you don't want to land in it. ; ) Also, if you are hiking in Scotland bring your rain gear and while I don't think that the midges are anywhere near as prevalent as people portray them, it is nice to have a midgie hat when you do run into them. ; ) (Good boots are important too that are waterproof. Lots of burns and lots of mires in Scotland. Pam

Re midges, this site gives forecasts on their likely intensity at any one time. http://2010.midgeforecast.co.uk/

Re: uk Avoid ticks (Lyme disease) - check yourself if going off track and wading into heather or working with sheep/deer. You can get treated, but the symptoms are wide ranging and realitively non-specific. Our ticks don't carry American tick borne encephalitis. Midges are pain as they are very itchy - if you're unlucky the bite will get superficially infected. You cannot avoid them. They occur near water and are worst around dusk/dawn and when the air is still (pray for rain on these days ...). Only summer months. You can only avoid them if you're in the city or out on the sea. Some people suffer more than others. I've been bitten 100s times. Adders are very shy - you won't see one unless you're lucky. There's tons of food for them so they're not very venomous. Re: general - probably want to ensure tetanus, etc is up to date. S

Ps Agree with Nigel on the dock leaf for the nettle. Pam - you will see black clouds of midges sometimes .... It's not a myth (I spent several weeks every year on the west of scotland as a child on hols as a child/teenager)...
S

I'm sure you are right about dark clouds, but ten or so hiking trips of a week each in the highlands and have used the midgie hat only half dozen times. I think I don't want to go walking with you tho Susan. Maybe they love you. ;). Of course, I grew up with Northwoods mosquito and those horrible black flies whose bites hurt!