The cardinal rule is everyone takes too much stuff the first time!! Don’t overload the bike and touring will be much more enjoyable. Remember the camping holidays you went on as a teenager, when you brought home half of your clothes unworn? Well don’t make the same mistake touring.
Don’t forget two things: You can wash/rinse out clothes and wear them again, and there are shops over there just like in the UK! You can always but a couple of 3 euro t-shirts or whatever in a hypermarket if you forget something. They even have pharmacies if you need over the counter stuff.
When touring the EU, a pair of light trousers and or shorts a polo/tee-shirt, fleece and a pair of trainers will deal with most evening activities and cut down on the amount of luggage you need to take. Hotels are very relaxed about bikers, even the posher ones we include in the tours. Thin fleeces can always be used to bulk up riding gear if the temperature drops dramatically during the day! Nice tee-shirts etc will only be worn for a couple of hours each evening so 3 or 4 is plenty for a 12 day tour. On bike t-shirts or under layers can be rinsed out every couple of days and dried overnight in the hotel bathroom.
In addition to what we wear for riding, we generally take just one posh tee-shirt/ polo shirt and one pair of non-bike socks per 3 days, one fleece/jumper for evenings one pair of smart trousers and a set of clean underpants for every day.
You don’t need a huge set of toiletries either. There is always shampoo etc provided in the hotels. Toothbrush and paste, any personal medication, a comb and a razor will probably be enough. Add some Paracetamol, Imodium and Strepsils and you are set.
As to packing we use one pannier for tools, first aid, emergency kit, over-suit, etc, and the other for clothes and toiletries. Tools etc go in the right hand side so that you are not standing in the traffic in Europe if you have to stop and get the over-suit out when the heavens open. We use cheap camping drybags inside the panniers to ensure everything stays dry. Additionally you can squeeze all of the air out when you seal them up, effectively vacuum packing the clothes s into a very small volume.
You must take the originals of all of your bike documents, V5, insurance, driving licence, breakdown insurance, travel insurance and obviously passport and also colour photocopies in case of document loss.
We recommend using ziplock plastic bags for very sensitive items eg electronics, documents, copies etc. We use freezer bags from IKEA which are available in A4 size with a double “zip” and are very hard wearing, opening and closing a dozen times with no issues.
We always take a tank bag, containing all the original documents you must carry, wallet, camera, etc. easy to remove and carry with you when stopping for a coffee etc. Keep the photocopies separate from the originals, eg in a pannier with the tools. Also in the tank bag the odd sandwich and snack. A refillable aluminium water bottle will save you a fortune in mineral water and helps you to stay hydrated every time you stop for a photo op.