*

FTSE 100 down 0.04%, FTSE 250 rises 0.5%

*

UK firms lose momentum as they worry about new tax hikes,

PMI

shows

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Kingfisher surges on raising full-year profit forecast

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Serco ( SECCF ) rises on $972 million US Air Force contract

(Updates after markets close)

Sept 23 (Reuters) -

London stocks ended mixed on Tuesday as investors assessed

an assorted bag of corporate earnings alongside economic data

pointing to a slowdown in British business activity.

The benchmark FTSE 100 was down 0.04%, while the

domestically focused FTSE 250 gained 0.5%.

A survey showed British business activity slowed in

early September, as companies reported a loss of momentum and

confidence given the rising risk of tax increases later this

year.

This follows Friday's report showing Britons have turned

more downbeat this month, with the prospect of tax increases in

Finance Minister Rachel Reeves' November budget threatening to

further erode confidence.

Last week, the Bank of England held its benchmark interest

rate at 4% and said it is monitoring for signs that inflation

pressures are waning before it reduces borrowing costs again.

In the market, the broader healthcare sector

declined 1.7% with Oxford BioMedica's ( OXBDF ) 6.5% loss after

the British cell and gene therapy manufacturer reported its

half-year results.

Eyes were also on GSK as U.S. President Donald

Trump's administration asked drug companies to be prepared to

ramp up production of leucovorin, a form of folic acid, as a

treatment for some autism patients. GSK previously manufactured

leucovorin and sold it under the name Wellcovorin.

Shares of the drugmaker fell 1.1%.

Keeping losses in check, an index of retailers' stocks

rose about 3.3%, boosted by a 14.6% surge in

Kingfisher after the home improvement retailer raised

its full-year profit outlook after a better-than-expected first

half.

Other major retailers also advanced, with JD Sports Fashion

rising 1.7%, Frasers ( SDIPF ) up 3%, and Howden Joinery ( HWDJF )

gaining 2.3%.

Serco Group ( SECCF ) was among the top gainers in the FTSE

250, up 4.7%, after a unit of the British outsourcing firm

secured a contract to provide training and simulator services to

the U.S. Air Force.

Engineering firm Smiths Group ( SMGKF ) reported profit and

revenue above market estimates, helped by strong demand for

upgraded baggage-screening detectors and a recovery in the

semiconductor market. Its shares hit an all-time high in early

trading but later fell 3.3%.