Just a couple of points.
FlyingforFun you said "I'm certainly not an aerobatic expert . . .". If you were you would know that the ONLY reliable way to tell the direction of a spin is to look at the turn needle and that the standard spin recovery is based on doing this. That is why, as Send Clowns says, the turn co-ordinator is such a dangerous instrument in a fully aerobatic aircraft. FNG, having flown an aircraft with an almost untoppleable AI (cost of AI/HSI around £100000), the old fashioned turn needle was still the recovery cue in a spin.
On the tech side, the turn needle and turn co-ordinator gyros actually spin a lot slower than the AI and DI. The reason is that the AI and DI rely on rigidity to give you the information you want and that needs a high rpm whereas the turn needle and co-ordinator rely on precession. This means that the turn co-ord or needle need only a low voltage DC supply to keep them working while the AI needs a lot of suck/blow or an AC supply (or DC plus an internal inverter).
Undertheweather. In answer to your question about keeping the TC as well as the TN I'd say no. The TC only has advantages over the TN if you plan on spending lots of time IMC with no AH. Under normal circumstances you're going to fly attitudes and ony use the TN to confirm that the AoB you're using is giving you a rate 1 turn. If you lose the AH then you'll be doing a little bit of flying on the TN to get VMC again so the slight loss of initial sensitivity to roll is hardly a big issue. If you keep both you could get very confused when they indicate opposite directions (as they will when you roll out of a turn).