I'm no expert but that's very difficult too answer.
I would say, if your thinking of a job on the horizon and are fit enough too be considering it do you think you'll pass a W.C.A ??. if you did and take on a job I'm not sure the legal implications of it would be favourable from the point of view of the DWP, they might and i say might ask for it back,because technically you've been saying your unfit, it make be the case your put in the working group too eventually in the future moving towards work if you still feel fit enough too do so given that PD is a degenerative illness.
there are rules you can look up on esa and working.http://www.disabilityrightsuk.org/work-people-living-disability-or-health-conditions
When i was assessed i was put into the support group, I was and am in the mind that i am not fit enough too consider working and was found too be just that for the foreseable future.