Are these stocks 'brilliant buys' after today's news?

Insurance giant Hastings Group(LSE: HSTG) leapt to fresh record peaks of 215p per share on Thursday, the shares rising 4% following the release of tasty financials.

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Hastings said gross written premiums surged 28% during the six months to June, to reach £360.6m, with live customer policies up 17% to 2.2m. This drove operating profit 20% higher from the corresponding 2015 period, to £70.8m.

The firm's core motor division continued to tear higher, and Hastings' market share rose to 6.2% in the first half from 5.5% a year earlier. But the Bexhill-on-Sea business is also making inroads in other markets -- home insurance sales surged by more than two-thirds between January and June.

And Hastings believes it has what it takes to keep this momentum going, the firm noting that "the UK leaving the EU is not likely to impact the need for UK motorists and households to obtain insurance and is therefore unlikely to significantly affect demand for the Group's products."

I reckon a forward P/E multiple of 13.9 times makes Hastings a great-value growth stock.

London stalling?

Property investment trust Derwent London (LSE: DLN) hasn't fared so well following its own update, the stock recently dealing 3% lower from Wednesday's close.

Derwent advised that letting activity hit record highs during January-June, the firm letting 267,700 square feet during the period.

But investors have headed for the exits after the capital-focused business downgraded its rental growth forecasts for 2016, Derwent commenting that "the outcome of the EU referendum may lower activity." The company now expects rental incomes to expand between 1% and 5% this year versus its prior estimate of between 5% and 8%.

Given the huge uncertainty swirling around the UK economy in the near-term and beyond -- and consequently demand for Derwent's office space -- I reckon the stock is an unappealing buy at present, particularly due to the stock's huge forward P/E rating of 35.8 times.

Financial flailer

Insurance leviathan Old Mutual(LSE: OML) also worried investors on Thursday with a patchy first-half update of its own. The stock was last dealing 6% lower on the day.

Old Mutual -- which had surged to 12-month peaks of 225p per share this week -- advised that "the macro-environment has been challenging with a weaker rand against the first half of 2015 and lower average market levels."

Adjusted pre-tax profit slumped 22% between January and June, to £708m. And the insurer warned that "an uncertain environment continues in our three largest markets of South Africa, UK and US which may lead to further challenges."

On the plus side, Old Mutual advised it remains on track to complete massive restructuring by 2018 that will see it split into four separate divisions.

I remain convinced that Old Mutual's focus on fast-growing African nations should deliver sterling returns in the years ahead, and that the firm remains decently-priced despite recent share price gains -- Old Mutual deals on a prospective P/E ratio of 11.8 times.

Still, I reckon the prospect of extra currency-related road bumps ahead, allied with further market troubles and possible separation problems, makes Old Mutual an unsuitable pick for risk-averse investors.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.