Heather's got a lot of experience of supporting. She tells me that she's spent three hours in a bed in 5 PBPs between the start and the finish, and that was in Tinteniac after she packed in 1999. The rest of her snatched sleep has been on tarmac, floors, or the back of a car or van while supporting me or filming.
She usually had a red 'Official' number on the vehicle, so could go onto the route, but her observations have general value.
You're only likely to average twice the speed of the rider by the time you've attended to all the things you need to do. So there's a need to look at how many of the controls you might cover. Look at the ones that that are nearest to trunk routes. Those trunk routes have changed over time, so don't work from historic accounts.
If you can't go onto the route, you're likely to see a much more modern France than the riders, which isn't always pretty. It can be soulless or run-down, sometimes both. It can be worth taking a bike, so you can park up off the route, and see some of the nice bits. Ambrieres, St Martin or Sizun fill the bill. That's if you've built up enough time.
Decide if you're providing somewhere to sleep for your rider. If it's in an estate car, you'll need to be very disciplined with your packing.
Engage with other helpers. Everyone has the excuse of looking after the needs of the rider if they need some me-time.
Getting anywhere near controls can be difficult, as barriers block the way. Sharing positions on smartphones will help you find each other. A sat-nav is essential.
it will be a lot easier if you've supported a rider on a 12 hour or 24 hour TT. Supporting a rider on PBP with no experience of other cycling events is a recipe for disaster. Heather had started two PBPs, and finished one, run a control on LEL in 2002 and 2005, supported me on 12s and 24s, and I'd supported her on a 24. I'd also completed two PBPs and two LELs prior to her supporting me on PBP 2007 with a press pass and red numbers on the car. That means that she had the spare capacity to look at what she was doing.
The potential to be overwhelmed by the process of supporting is large, and there'll be some bickering and recriminations along the way. That's part of the fun.
The finish in 2015 was a pretty lame affair. Prior to that it was bit of a carnival atmosphere. Hopefully, 2019 won't be such an anticlimax. The finish is as important for supporters as it is for riders.