OK I am steering clear of matches involving India for now.

After taking a first innings lead of 125, Sri Lanka are now 300 ahead in the 2nd innings and still have 1 wicket left.

The highest 4th innings on this ground to win a test match (if my facts are correct) is 96 and the highest 4th innings total is about 250

Yes there are 2 and a bit days left of this Test Match but can England really chase down 300+ ?
Unlikely

Their highest successful chases to win a Match have been
332 against Australia in 1928
315 vs Aus in 2001 - Headingly
307 vs NZ in 1997 - Christchurch
298 vs Aus in 1895 (yep not a typo) - Melbourne

And England are 3.5 on Betfair
Would recommend the lay for 8 units
Upside 8 units if SL win or a draw
Downside 20 units if England win

Good luck