Firstly, it is worth clarifying that under the law, to be eligible for work JSA claimants have to demonstrate that they are available for work. But what the automatons at the Jobcentre or Working Links tell people is necessary, is somewhat different from the measures prescribed in law.

Whilst, I am not a fan of statistics myself these particular ones that follow are pretty solid, in that they do actually relate to what happens day in day out on the ground. What is demonstrably proven here is that when people appeal they are successful far more often than not. The stats have been taken from DWP and the link to the tables is here.
 http://83.244.183.180/sanction/sanction/LIVE/tabtool.html

Variable sanctions
These can last for between 1 and 26 weeks. From April 2000 to July 2007, a total of 2 686 400 decisions were taken to impose a sanction of this type. In the vast majority of cases (2 665 710) no appeal was made. This is partly because upon reconsideration of the original decisions only 312 720 were upheld.
However, for the 20 690 appeals that were made, 17 920 were in favour of the claimant. This works out at 86%.

Fixed sanctions
A sanction of 2 weeks (4 weeks if repeated within 12 months, and 26 weeks if already received a 4 week sanction within last 12 months) are imposed for refusal, without good cause, to attend an employment programme or carry out a Jobseeker’s Direction.
Of 500 790 sanctions only 38 890 were upheld on reconsideration. There was a total of 3500 appeals. Only 130 went against the claimant. That is a 96% strike rate!
Broken down into the reasons given for the sanction, cases in which claimants had given up a place on an employment training programme there were 260 appeals and only 10 went against the claimant.

Entitlement decisions
There were 1 623 630 decisions that people were not entitled to JSA. There were 6940 appeals. JSA claimants lost only 260 cases. For example, looking at the reasons given more closely of these appeals, benefits were stopped in 3350 cases for Failure to attend/ Failure to produce signed declaration. Only 80 decisions were upheld before the tribunal.

These stats only reinforce the need to challenge these decisions whenever they are made. If more people appealed Jobcentre plus could not possibly impose so many sanctions in the first place as the system would crack under the strain.