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* FTSE 100 down 0.5%, FTSE 250 down 0.1%

* Tech stocks lead gains ahead of Big Tech earnings

* Ryanair falls after profit slump, fare warning

* Andy Burnham takes office as Britain's new prime minister

By Tharuniyaa Lakshmi

July 20 (Reuters) - London's FTSE 100 edged lower on Monday

as U.S.-Iran tensions fuelled concerns over shipping through the

Strait of Hormuz, while investors looked ahead to policy signals

from new British Prime Minister Andy Burnham.

The blue-chip FTSE 100 index fell 0.5% to 10,543.91

points by 1052 GMT, while the midcap FTSE 250 slipped

0.1%.

* U.S. strikes on Iran entered a ninth straight day, and

risks to shipping through the Strait of Hormuz mounted after

reports of tankers being immobilised. Brent crude prices climbed

above $90 a barrel for the first time in a month.

* Energy-price-sensitive sectors such as automobiles

and travel and leisure fell 1% and

0.7%, respectively, as rising oil prices heightened concerns

over costs and consumer demand.

* Investors also monitored the political transition in

Britain, where Andy Burnham was set to become the country's

seventh prime minister in a decade, succeeding Keir Starmer with

promises to tackle living costs and struggling public services.

* "Political change is a lot for investors to digest, but

they've got more on their plate. The Iran war has escalated and

driven oil prices back above $90 a barrel. That means inflation

fears are back on the table, which has major implications for

interest-rate expectations," said Russ Mould, investment

director at AJ Bell.

* British government bond yields edged higher, as investors

assessed the implications of a new Labour government for fiscal

policy and public spending priorities.

* Meanwhile, technology stocks rose 0.5% to lead

sectoral gains ahead of earnings from U.S. Big Tech companies,

which could provide a fresh test of the AI-driven rally.

* Ryanair tumbled 7.2% after the budget airline

reported a one-third drop in first-quarter profit and warned

summer ticket prices could come under pressure amid uncertainty

over the Iran conflict and the broader economy.

* Shares of Big Yellow ( BYLOF ) dropped 2% after the

self-storage firm reported a decline in first-quarter occupancy

rates.