The following registrars are currently taking pre-orders on .uk rights:

Update 2nd June: Registrars no longer taking orders are striked-out below
Price: £9.99 per registration
Live Registrations, first come, first served
Price: $79 USD on successful catch
See Reserved .uk release for more details.
Price: £4.99 + VAT on successful catch (top up required).
You can submit 50 names in the
dashboard here.
Price: The minimum price for a backorder is £50.
See: .UK Nominet Release
Price: auction rules apply
.uk Expired Domain Auction
Price: Standard .uk price applies
See: End of priority registration for .uk. What’s next?
Price: The regular .uk price scale applies.
Details: You can transmit your .uk applications as of Wednesday, June 12, 2019 (12:00 UTC).
RRPproxy allow more than one application per name and you can not check to see if slot is taken.
The Application filed first, will be processed first.
See Newsletter & Wiki for details.
Price: Free to pre-order. £70.21 on successful catch.
Details: Go to the .UK Special Release Droplist
Contested names go to Closed Auction (more than one).
Price: £19.99 + VAT per pre-order
Details: Scroll down to see the pre-order list
Price: £4.99 + VAT per pre-order
Details: Need to go to the site to pre-order
Contested names go to Closed Auction (more than one).