Who is/are the child's Trustee (s)?
It would appear that the lump sum has been left to the child unconditionally/ is a death lump sum from a pension?
If so, this means that the child owns the money and is only prevented from taking control by virtue of his minority and the money needs to be held/invested in Bare Trust.
However, be sure that the nature of the Trust is clarified.
It might be as well for you/the child's Trustee (s) to take professional financial advice from an Independent Financial Adviser if the lump sum is to be invested, rather than held in cash deposits.
It is possible to hold an investment account in Bare Trust for a child.
It should be possible for the child's Trustee to open a bank account into which the Â£200,000 can initially be deposited and which can accept the Â£1000 a month.
The Trustee should consult his own bank and explain the situation or might try Barclays, HSBC or Metrobank.
might offer a temporary resting place.
The child is likely to have a CTF - see here re transfer to JISA -
The above could hold Â£8080 this year and then the Trustee can continue to move in a lump sum each year until the child turns 18.
Make sure that you/the trustee understands the taxation of income/gains from a Bare Trust or from whatever type of trust is involved