Pension/ISA Question

[Spydaman]

Probably an obvious question but just want to be sure before I do anything rash. I've got a personal pension through work which I pay into, the company tops up and I pay AVC's. I've also got a cash ISA with some money in. I'm coming up 52 and would retire tomorrow if could. Am I correct in saying that if I pay a lump sum into the pension this gets topped up at my income tax rate. If it is why should I keep any money in the ISA (except for emergencies) earning a paltry 3% when I could get an instant 20%. I appreciate it would be tied up until I'mm 55 but that's not long for me. And I could then take out 25% tax free. It seems to me that I should be putting every spare penny into my pension.