* SJP shares down 5%, peer Jupiter falls 10%

* SJP posts rise in FUM, but net inflows halved y-o-y

* Says new fee structure to reduce ongoing charges for existing investments

Oct 17 (Reuters) - St. James's Place on Tuesday said it will change its fee structure for most new investment bonds and pensions to comply with new UK rules.

In the last couple of years the UK wealth manager has seen client inflows slow and regulators crack down on high fees.

Last week, it said it was working with regulators and evaluating its options in response to rules set out by the country's finance watchdog.

The FTSE 100-listed wealth manager said the revised structure will consist of an initial charge and ongoing charges but without early withdrawal fees or a gestation period for a vast majority of investment bonds and pensions.

Furthermore, charges across all its wrappers - assets grouped into single securities - will now be separated into component parts instead of being grouped into an all-inclusive disclosure.

The changes are aimed at reducing overall ongoing charges for existing investments across core products and will come into effect in the second half of 2025.

The changes will reduce the group's underlying cash for the next few years, SJP said in a statement.

Its shares were down 5.2% to 637 pence in early trade. They have lost 40% of their value this year.

The company said its funds under management at end-Sept. stood at 158.57 billion pounds ($193.25 billion), up from 157.5 billion at the end of June.

However, third-quarter inflows more than halved from a year earlier to 0.91 billion pounds.

Smaller rival Jupiter Fund Management reported a fall in its third-quarter assets under management to 50.8 billion pounds, citing muted retail investor appetite, which sent its shares down 10.6% in early trade.

($1 = 0.8205 pounds) (Reporting by Eva Mathews in Bengaluru; Editing by Nivedita Bhattacharjee)