Might be better posting in the Pensions forum.
If scheme rules allow and Trustees agree then yes for retirement at 55. In a DC scheme can't see why Trustees would not agree. Employer agreement may also be needed depending on the rules.
700k sufficient for what ? There are many options available within a DC scheme, tax free lump sum/annuity/ARF. And many personal things to consider, outgoings/savings etc. May well be worth investing in some personal fee based financial advice.