This is a bit of a datadump, it's information accumulated that I've posted on line elsewhere, but ought to here.
Using the defence plans for Canada, and the Hydrographer's report to Adm. Milne we can estimate the British Royal Navy force that they planned to use in the event of war with the United States.
WO33/11 gives the planning figures for the defence of Canada:
At Quebec: 2x line of battle and 1x ironclad battery
Operating between Quebec and Montreal: 2x ironclad battery, 2x corvettes (noting a maximum draught of 18 ft), 2 dispatch vessels and 7 gunboats
On Lake St. Francis: 4x gunboats
On Lake Ontario: 3x ironclad battery, 4x dispatch vessels, 16 gunboats
On Lake Erie: 3x ironclad Battery, 20x gunboats
On the Richelieu River: 6 gunboats
Total for the inland seas of Canada: 2 line-of-battle, 9 ironclad batteries, 2 corvettes, 6 dispatch vessels, 53 gunboats = 72 vessels
Three of the nine ironclads were to come from the existing Crimean War ironclads, probably as only one (HMS Aetna) can actually transit onto Lake Ontario (she just squeezes into the locks with 6 inches to spare at the beam). None of the batteries have engines strong enough the run the rapids. Six of these ironclads are available for service (Meteor is already uncased and awaiting wrecking, Trusty has been converted into an experimental turret vessel and is likely too unstable to risk at sea). The cost of these six new ironclads was set at £300,000 for all six, slightly cheaper than the ironclads of 1854-5. Build time was to be 90 days.
The force recommended by Captain Washington to blockade the Unites States was:
Penobscot Bay: 2x sloops, 2x gunboats
Kennebec River: 1x sloop, 2x gunboats
Portland: 1x frigate, 2x sloops, 2x gunboats
Portsmouth, NH: 2x sloops (and notes the defences mean a mortar vessel can range on the navy yard without any return fire)
Salem and Marblehead: 1x sloop
Boston: 1x line of battle, 2x frigates, 2x sloops, 2x gunboats
Nantucket Island: 1x frigate
Narrgansett Bay: 3x sloops, 3x gunboat
Long Island Sound: 1x line of battle, 1x frigate, 2x sloops, 2x gunboats
New York Harbor (South Entrance): 2x line of battle, 2x frigates, 2x sloops, 2x gunboats (much ink is spilled over how to attack New York)
Delaware River: 1x line of battle, 1x frigate or sloop, 2x gunboats (4 if possible) (much ink is spilt noting that a gunboat flotilla could penetrate up the Delaware as far as Trenton, NJ, and that a gunboat force on the river could destroy the Dupont powder mills, smash Philadelphia and other such nastiness)
Chesapeake Bay: 2x line of battle, 2x frigates, 6x sloops, 6x gunboats
Port Royal, SC: 1x frigate, 1x sloop
Total blockade: 7x line of battle, 12x frigates, 25 sloops, 23x gunboats = 67 vessels
This didn't include a cruising force of 25 vessels of the West India Squadron. Nor does it include Milne's planned particular service squadron, which was to include Warrior, Black Prince, Defence and some other ironclads (probably the available three), plus some line of battle and a large gunboat force. This last force was the most worrying, Milne planned on reducing coastal fortifications (starting with Fort Monroe and moving into the Chesapeake) and sending gunboats up the navigable rivers to destroy everything that was shellable. Unfortunately for the US that is quite a lot of war industries.