The index rose 1.1% after encouraging US job data calmed investors' nerves but the bourse still posted its worst week since that of Oct. 12 last year.
The UK-oriented FTSE 250 climbed 0.7%, led by gains in power generator Drax after sources told Reuters the European Commission was set to approve Britain's roughly one billion pound power backup plan.
Blue-chip peers SSE and Centrica also gained.
A parade of weak readings on services and manufacturing sectors from multiple major economies has left little doubt that the US-China trade war has constricted global growth.
However, a report that showed moderate US job growth in September and unemployment rate that dropped to a 50-year low, helped soothe fears and spurred buying in stocks.
Investors also grew hopeful that central banks will step in with further stimulus. The Federal Reserve - the world's biggest central bank - has already cut interest rates twice this year.
"As for the Fed, this (US job) report doesn't really shift the needle too much - not so hot to force a rethink on cuts, but not a disaster that could ramp expectations for more aggressive easing," said Neil Wilson, analyst at Markets.com.
At home, investors remained worried about London's ability to secure a Brexit deal with Brussels at a summit later this month, with the state of the UK economy appearing to have slipped into recession also adding to anxiety.
The FTSE index of 100 most valued UK companies had fallen as much as 160 points below its 200-day moving average on Friday despite gains and has lagged other major markets this year, underlining the additional turmoil Brexit has brought on.
"There's precious little positivity around UK stocks - Brexit uncertainty, profit warnings aplenty, CEO purges, weak UK data and a slowing macro picture for the heavy weights exposed to global growth adds up to a pretty disappointing near term outlook for the FTSE," Wilson said.
In corporate news, BP became the latest blue-chip company to name a new top boss as it said upstream business head Bernard Looney would succeed CEO Bob Dudley, sending its shares up more than 2%.
Tobacco giant Imperial Brands and retailer Tesco also announced CEO departures this week.
LSE advanced nearly 3% after a Reuters report that some of its investors had asked Hong Kong Exchanges and Clearing to sweeten the takeover bid.
Insurers ended on a positive note after Britain's markets watchdog threw down the gauntlet, saying they could avoid mandatory pricing restrictions if they voluntarily stop penalising loyal customers. The sub-index earlier touched its lowest level since February on fears of such restrictions.