Short tour on a road bike, who's experienced?

Thanks!

Sorry I was being terribly general but fishing for just the kind of answer you gave. I think it's doable with the saddlebag alright, and investigating ultralight tent and compact sleeping bag options. Having a look at your idea about alpkit bags now too. Municipal campsites look the biz and for a couple of euro! Great stuff.

I presume a few people have taken the sail/rail from Dublin to London, perhaps London to Calais too, just wondering if there are any things to be aware of as a cyclist with a bike on these trips - is the bike locked up below decks and are there separate carriages on trains for bikes etc? Apologies if these questions are annoying but there's very little info apart from costs on the official websites (and even those are a little vague for some services).

Thought I'd post a follow up here for anyone interested in lightweight touring/camping.

Thanks to your suggestions, especially ror_74 for all the advice. I bought a Carradice Camper Longflap with QR support as a saddlebag - my Lapierre doesn't take panniers so the combination saddle & seatpost support works well. I also bought a Carradice carradura handlebar bag.

My weight limits were approx 10kg on the rear and around 5kg on the front and space was also at a premium.
Eureka Solitaire 1-man tunnel tent.
Snugpak Travelpak 1, 3-season, compressions sack sleeping bag.
Zip-off travel trousers/shorts.
Microfibre towel with click latch so i could let it dry while cycling.
10L dry sack (stuff sack) compression bag for my clothes around €15-€20 lots of brands.
Argos camping mat.
Power bank to charge phone, gopro and vaporiser.
Kryptonite mini-ulock with mount bracket.
Had a fairly extensive service on the bike which unfortunately meant new wheels, new brakes and I changed the rear tyre to a 25mm gatorskin for more comfort than my 23mm. As well as bringing 2 tubes, plastic tyre levers and 2 bottles of gas & adaptor I taped a spare gatorskin tyre under the down tube. I had two sets of cycling gear, and 3 sets of t-shirts/underwear with a merino top and leggings that could double as casual wear with my travel pants. One hi-viz rain jacket (vital in the bad weather I had) a pair of penneys €4 plimsols.

My plan was to get to Luxembourg for pints with my cousin. I bought a sail/rail ticket from Irish Ferries for €131 to include my bike in a return trip to London. I'll probably not ever go through Britain again if possible. The rail system there is beyond useless. Multiple train companies with different policies means that what should be a straighforward trip from Holyhead to St.Pancras is instead a nightmare of running down platforms with a fully laden bike and throwing yourself at the mercy of engineers who can decide on the spot whether or not to let you on. No reservations can be made at all with some services. In the end I think I took 7 trains to get to Dover.

Word of advice about Calais. Don't arrive at night. They've shut the terminal which used to be 24hrs and is recommended on travel forums for 'friendly staff, showers, all night food' so I found myself being told to leave the port at 2am into a thunderstorm and with no hotel rooms available. I had to rest in a bus stop in the centre of town while hurricane Bertha and dodgy people kept me from sleep.

In France, cycling is a real pleasure. The drivers almost without exception gave me wide berth, backed off on hills and junctions and even waved encouragement from time to time! Maybe I was fortunate in that my route included many towns that had been visited by the Tour this year. Similarly, the trains are accommodating. There is no charge, no reservation necessary and many trains have between 6-12 hanging racks for bikes, even when there are only 2-3 carriages. (TGV has different rules and charges). As well as the roads being cycle friendly there are many bike routes such as the canal tow-paths that have been converted for a really low-stress cycle.

Camping: generally you don't need to book outside of high season if pitching a tent, I cycled in August and still had no problems. there are something like 4,000 campsites in France, almost every town has a municipal camping and on the whole I found them cheap and friendly as well as very clean. Standard price to pitch was €7-€10 including electricity. Private sites were more. The area of northeast France wasn't so suitable for rough camping as agriculture dominated so fields were either high with corn or full of cattle.

I'll throw a few pics below to show the setup I had. Hope that's of interest to people.
Fully loaded, saddle bag with the tent and floor mat under the long flap.

Bike racks in French trains, each with a fold down seat for cyclist beside it.

Sometimes the GPS took the piss

waterproof foldover for the map, takes pressure of constantly referring to gps

Typical of the overtaking was the cars actually took the other side of the road.

1-man tent. once you get organised there's plenty of room, however you can't really sit up straight in it never mind stand!