It does not matter hugely between income and accumulating, but if you plan to regularly withdraw money then I think the income version might be slightly better for you. If you agree with that after reading the following, you could keep what you already have as-is but put new investments into the income version again, and that way you can avoid lots of switching back and forth.
The difference between the two fund structures is that with income, any income paid by the underlying investments (for instance interest and dividends) gets redistributed out of the fund to the holders (possibly within the ISA or pension but as cash), but no underlying investments get sold. Whereas with an accumulating fund, any dividends or interest paid by the underlying investments into the fund get used instead to purchase new investments within the underlying fund, with no cash distributions by the fund.
The difference is subtle, but it means that unless you get the math exactly right regarding how much cash to take out, there is a certain likelihood that you will end up as a net seller of shares at exactly the wrong time (ie when the market is at a lower level) because it takes more shares to get a certain amount of cash.
With an income fund, the fund normally just works out how much cash it can give you without selling any underlying investments, and gives you that amount of cash while holding on to all investments. In the current market environment, in a stocks and shares fund you'd probably get something like 1-2% of the invested principle each year. If the market tanks, the income would probably be more stable than the market, which might also make it easier to avoid panicking and hang on.
I had previously assumed perhaps in error that your plan was to just leave the money in for a number of years, in which case it would not have mattered that much whether you chose income or accumulation.