in this day and age many riders have a gpx so it's easy. In which case the info control as we know it is often useless in maintaining distance integrity...
It'll only work when all riders have a GPS (very unlikely), or Audax UK have enough key loggers that they can be distributed to organisers.
Looking back at some of the results you find this weekend in 2010:-
10-759 Hailsham 306 17 Apr 21
10-119 Wolverley 305 17 Apr 87
10-91 Alfreton 212 17 Apr 53
10-751 Midhurst 112 17 Apr 33
10-164 Alltwen 201 17 Apr 12
10-644 Galashiels 202 18 Apr 34
10-714 Woodham Mortimer 106 18 Apr 47
10-664 Bishops Lydeard 113 18 Apr 12
10-162 Hebden Bridge 110 18 Apr 162
10-715 Woodham Mortimer 202 18 Apr 36
10-904 Bishops Lydeard 216 18 Apr 17
10-125 Shenstone 160 18 Apr 67
10-663 Bishops Lydeard 114 18 Apr 53
10-102 Maidenhead 104 18 Apr 43
10-166 Woodham Mortimer 156 18 Apr 40
10-126 Shenstone 213 18 Apr 17
10-161 Hebden Bridge 53 18 Apr 47
10-124 Shenstone 102 18 Apr 136
10-662 Bishops Lydeard 64 18 Apr 7
10-92 Maidenhead 62 18 Apr 10
That's a total of 934 finishers over a single weekend. At £25 a pop that's close to £25000 of key loggers if you assume there were 1,000 starters and only ~5% DNF.
That's a lot of extra stuff to have to keep posting around between organisers, especially if they need to be insured each time they're posted, etc.