Job Done!
After 4 days of peddling we finally cycled through central Paris on Saturday afternoon, arriving at the foot of the Eiffel Tower around 5pm.  The total distance travelled in the saddle since setting out from Croydon on Wednesday morning was about 300 miles (including a slight detour when one of the route markers mysteriously disappeared).  
Although the weather on the first day cycling through the UK was pretty good, there are some tough hills in the south downs and before lunch I was seriously doubting whether I'd make it all the way. But the afternoon run down to the ferry felt easier as I got into the rhythm. The ferry from Newhaven to Dieppe was late, and we didn't make it to the hotel until nearly midnight. Worse still, with 100 people all trying to take showers at the same time, the hot water disappeared almost immediately, so it was a cold shower only that night.  
That was just a foretaste of things to come, though.  The next morning we had to leave at 7:30am, so after only a few hours sleep we were facing an 88-mile ride. And it was raining! Not just a shower, but a heavy 45-degree cold, driving rain that soaked through to the skin before we'd even lost sight of the hotel. The rain carried on for the next few hours, and it wasn't until the lunchtime stop after 48 miles that I was able to get a hot drink and wring out my clothes.  The hills between Dieppe and Lisieux (where we stayed the next night) seemed endless, especially in the wet. But later on the sun came out and it even got warm towards the end of the afternoon, so that I was almost dry when I coasted down the long hill into the town centre around 5pm.
A slightly later start to the following day was appreciated, though at 8.30am when we left, the skies were darkening again. We also had to climb back up the steep hill we'd free-wheeled down the day before in order to rejoin the route.  Within minutes of setting out, spots of rain were felt, and shortly afterwards the rain started again; first a light drizzle, then a torrential downpour which didn't seem was ever going to stop. It was so heavy that several of us took shelter under trees, hoping it would quickly pass. But being already soaked and not moving, we just got colder and colder, so that after 15 minutes it became clear we'd just have to ride through it or suffer potential hypothermia.  That was probably the lowest point of the trip for me - we'd only covered about 10 miles and the rain seemed as if it would go on all day, so although you were not getting colder while you were moving, you weren't warming up or drying out either.  By the time we reached the morning water-stop, the rain had gone and  I was able to wring out my clothes before heading off again (still no hot drinks, though).  The sun came out, the terrain became  gently undulating, and by the lunchtime stop it actually felt like summer.  The rest of the 73-mile journey to Vernon (the next overnight stop) seemed to pass really quickly and we arrived far earlier than anticipated.
At the start of the final day I was expecting the worst again, but finally the weather we hoped for arrived and the whole atmosphere changed. With a mere 65 miles to go to Paris, and the steepest hills near the start of the day's ride, people were happy to take it easy, and we even stopped for coffee at a cafe along the way. (Their takings must have been well up that morning!)
As the countryside was slowly replaced by suburbia and the roads got busier it felt more like cycling at home. Roadsigns for Versailles and Paris gave an extra boost, and we soon reached the final drinks-stop on the edge of Paris where we all had to assemble before the final 5-mile escorted ride into the city centre.   We seemed to be quite a tourist attraction, with everyone in identical blue T-shirts cycling slowly through the streets, across the Place de la Concorde, around the Arc de Triomphe and finally along the banks of the Seine to the foot of the Eiffel Tower, the official end-point of the ride.  After a plastic-cup of champagne and a few photos, we cycled a couple of miles to the hotel and left our bikes to be transported back to London.
A special celebratory meal in the hotel, followed by all the alcohol we'd been denying ourselves earlier in the week and a long lie-in the next morning rounded off a tough but enjoyable trip.  
Since the Eurostar back to London wasn't until after 6pm, the whole pace of Sunday was different. I spent the day being a very lazy tourist, taking a river cruise and watching the sights drift past without any effort on my part.
The Eurostar service to London is amazingly fast now, and we were back at St Pancras where our bikes were waiting by 7:45 London time.  Duncan Evans (also from Kew Wind Orchestra) & I both set out to ride across London to Waterloo with the intention of taking the train to Twickenham, but as we crossed Waterloo Bridge we decided we'd cycle the final 12 miles instead, so I finally reached home just before dusk.

Thanks again to everyone who's sponsored me. The total I've raised stands at around 1,300.  If anyone would still like to donate, it's possible to do so here. I've paid all the fees and administrative costs of the trip myself, so anything you donate will go entirely to the charity to support their work.

Chris.