It is usually possible to take pension benefits at age 55 and typically 25% of the fund can be paid to you as a taxfree lump sum.
However, I think you are referring to triviality rules, where small pension pots can be paid out completely in cash. This can only be done from age 60 and then only for those with total pension assets below, currently, £18,000, or individual pension pots worth less than £2,000. While 25% of the cash sum is usually tax-free, the remainder is taxable as income.
If you do remain in the company scheme then it is likely you will continue to pay charges. However, you will also pay charges if you are in a new scheme and so you should look to compare one against the other.
Also, while your pension may have performed poorly, this is likely to be a result of the funds you are invested in rather than the policy itself. You should investigate to see if you have other fund options within your current pension.
If you are considering a pension transfer, particularly from a company pension scheme, you should take independent financial advice first. This will ensure transferring is right for you and that you won’t lose any valuable benefits or guarantees.