You can buy up to about an extra £7K pa in LGPS which will take most of your £100K
Given that you are close to retirement age my immediate thought might be to think about what you currently have and what you might need in retirement.
You dont necessarily have to tie the money up in a pension. Clearly you will need to buy some 'big ticket' items between your retirement and well, death/incapacity eg a car - or two, you will probably need to do some house maintenance/improvements etc etc etc
You may also want to consider what happens if you die 'prematurely' in which case the unspent money can go to your partner or children. By the same token you can live too long........
Your pension funs should offer you some 121 time with an adviser who can take you through the ins and outs of whats available.
If you dont mind me asking what is your current pension worth and whats your retirement date?
Do you have a partner in which case how are they placed?
If you want to take an income at 60 then if the money isnt in a pension plan then you can do what you want with it.
Finally of course if you put the money in a pension plan you might get tax relief BUT the income is taxable BUT in an ISA you dont get tax relief on the contributions BUT the income is tax free
Decisions Decisions