Martyn,
I am saving, but a new house and LifeForce probably will have to come first.
As for the Aikido, there are three aspects that are required for success.
1. You can buy a PCB for either 8 or 9 pin tubes, I chose the octal. Sourcing parts is easy. Part choice is a little fluid, but some advice is given, it mainly depends upon required amplification factor and the DC voltage to be used. The GK-1 uses unity gain, and as Hugh knows his stuff, I also aimed for low gain. I think that I have a gain of around 9dB, which is quite a lot more than unity, but still relatively low by preamp standards. Hugh once told me that the AKSA 55 can use a little active preamplification. Soldering onto the PCB is easy, although the PCB is printed on the upper (chassis) side, so I put the parts except for the sockets on the backside, so that I could tweak without removing the PCB from the chassis.
2. Chassis building. If you have the tools, it's easy. I find aspects to be a pain in the neck, other parts are relatively simple.
3. Power supply. I made this into a huge pain in the neck. There are simple circuits that use diode rectifiers and simple cap/resistor filters. I chose to use a diode bridge but with a choke / capacitor filter system. The biggest problem was that I purchased 20H chokes, and given that the current draw is quite low, they initially didn't perform as they should Argh! I learned a lot, added dropper resistors. Built a good ground lift circuit, and eventually added regulated 6.3VDC for the tubes. I did find members of the Tube forum on Diyaudio to be a good source of information and help.
The Aikido sounds great. Is it as good or better than a GK-1? I have no idea, but being a cheapskate, the Aikido cost me a lot less, afterall I am still saving for my Morgan (sorry I meant LifeForce

).
Without knowing anything about the GK-1 preamp, if it is anything like Hugh's AKSA amps, then it is of impeccable design and sound. Furthermore, the kit will come with well-sourced parts, and assembly instructions that are second to none. Further to the furthermore, Hugh and other forum users will answer questions promptly and clearly.
If you're doubtful about building a tubed preamp, and can spare the extra money, I would go with Hugh's GK-1. As I am sure you'll not be disappointed. You could always build an Aikido as a second project and use the best in your main system and maybe sell the other one.
Hugh, I hope you don't mind me posting about a preamp other than an AKSA one here. If you do, then I apologize.
Regards,
Charlie