Reliable cashback npower?

MatB

Coming to the end of Scottish Power's Online Energy Saver 6 at the end of the month, it looks like npower's Sign On-Line 19 is the best deal for me.

For dual fuel, the MSE Cheap Gas & Electric article suggests:

• SimplySwitch pays £35 in Amazon or John Lewis vouchers
• Energylinx pays £34 in cash
• Moneysupermarket pays £30 in cash
• SwitchwithWitch pays £20

I was going to go with EnergyLinx, but then realised I had to mail the supplier's confirmation of change in myself. This put me off as its a bit like the Mobile Phones cashback business. I guess they're hoping people will forget. Presumably email is sufficient?

I can get £40 from Top Cashback, but am wary of the comments on there that it takes months and months of claims to get sorted. This seems to be due to npower rather than Top Cashback, so can I expect all of the above to be fairly slow in paying up? Are any more reliable in actually paying up than others? I'm willing to forgo a few quid cashback for an easier life. I guess I've already spent longer than my time is worth tonight faffing about.