Borderlink, which trades as GoFibre, has received a further £164m investment from Gresham House to accelerate its full fibre rollout in Scotland and the north of England.
Toob's FTTP rollout in the south west has been given an £87.5m funding boost by Sequoia Economic Infrastructure Income Fund.
The new funds, on top of £75m invested by Amber Infrastructure Group in 2019, will fuel the altnet's ambition to pass one million premises by 2027.
CEO Nick Parbutt said: "With this investment we will expand into more towns across the south of England, bringing the benefits of full-fibre broadband to more families, businesses and communities."
Earlier this month, Sequoia invested £60m in LightSpeed, an altnet rolling out full fibre in South Lincolnshire and West Norfolk.