Six major projects at heritage sites across the UK are in line to receive a share of a funding package worth £21m following the Heritage Lottery Fund's (HLF) latest round of confirmed awards.

Three further schemes have also been awarded first-round passes by the funding organisation, which indicates initial support for plans that will now be able to progress to the next stage of development ahead of a final decision.

Among the six projects to benefit from the confirmed awards is the creation of a new interpretative centre and the preservation of 1,200 trees at Epping Forest, Essex, which will receive the largest grant, worth £4.76m, while the restoration of St James' Priory in Bristol has been awarded £3m.

Plans to guarantee the long-term future of the 23-hectare (57-acre) Great Dixter house and estate in Northiam, East Sussex, which was home to gardener Christopher Lloyd, will benefit from a £3.79m grant, with £4.53m awarded to a scheme to double the gallery space at the Scottish National Portrait Gallery in Edinburgh.

A scheme to develop a park at Castle Hill, incorporating the repair of the Knox Hannyngton towers, and the revamp of Ranfurly House in Dungannon, Northern Ireland, has been awarded £2.24m, and the establishment of a new 'Experience Barnsley' museum and archives centre in Yorkshire has secured £2.6m funding.

Dame Jenny Abramsky, HLF chair, said: "During these tough economic times, we still need to enjoy the things which enrich the quality of our daily lives – whether it's a beautiful garden, a gallery full of wonderful paintings, or a much-loved historic building."

Included in the first-round passes is Southampton Sea City Museum, which has been handed £499,000 to develop its application for funding worth £4.5m and the Abbotsford Conservation and Presentation Project in the Scottish Borders, which will receive £144,000 with a view to a potential grant of £4.44m.

Westonbirt Arboretum in Gloucestershire has also been awarded a first-round pass, with the HLF contributing £177,800 towards the development of an application for £2.8m.

Abramsky said: "These three projects really captured our imagination. They perfectly demonstrate the breadth of the UK's heritage and its importance to people. We have given them our initial support and look forward to seeing how they progress their plans to the next stage."