First I wouldn't build anything above a destroyer, immediately negates the value of the British Battleships due to lack off suitable targets. With their escorts this is about half the RN defeated without a shot fired. No admiral is going to send HMS George V or HMS Hood to hunt down a DD or S-Boat. Nor with some basic precautions are they going to attack your shoreline or coastal mercantile traffic. Just way to much risk against little reward.
However the RN will still need to maintain and expand its fleet of Capital ships due to both external (Italy & Japan) and internal factors(shipbuilders & admirals). This will also aid in keeping the sleeping dogs, sleeping. The British public will be a lot less worried about Germany if there isn't a HSF version 2.0.
Second go with commercially hulled & powered mine layers/sweepers and escorts. Or at least have conversion kits ready to be installed once war breaks out. Again due to these 'kits' being stuck in a warehouse they remain invisible to the British public even the professionals will have trouble spotting them.
Third the Destroyers job will be to hunt RN MTB, Destroyers, and Mine Layers to keep them away from your coastal shipping. Equip them as such and if you can make them coal powered with out losing combat efficiency so much the better. If possible make them appear as escort vessels by leaving off the torpedoes which wouldn't be of any use in their assigned task anyway.
Fourth the S-boats make sure that these officially do not have the operational range to reach the British coast from German harbors. Also call them Baltic patrols ships everything to imply that they can't harm the UK. But have plenty of these, a hundred or so re-based to the Belgian coast right behind the advancing Panzers is going to make any sort of Dunkirk evacuation impractical.
Fifth Merchant Raiders, again completely undetectable before the war, just make sure that they are out on the oceans just before the war breaks out. Take some 20 year old cargo vessel cram it full of coal and slap on some torpedo tubes and a gun or two and off they go. If they manage to sink even one Allied ship you are already far into the black, actually even without sinking anything they will already eat up RN resources as cruisers will have to be sent out to hunt them down. However should they be sunk/captured it is no great loss to Germany.
Sixth and final the submarines, try to hide them as best you can. Concentrate more on enabling rapid and continuing expansion of this fleet then having lots of them ready on day one. This will be a game of attrition.
Extra ideas
-announce and make much of the fact that Germany will refrain from building any offensive naval vessels.
-make arrangements to transport the Swedish iron ore via the Baltic during the summer months.
-buy as much crude oil before the war as is possible, store it in the old salt mines. At $0,10 a gallon it is steal at twice the price.