I am wanting to purchase an A-frame to tow my series 111 Alpine. Does anyone know if I need a specific type for my car, or if any A-frame will do?

May I suggest you contact the club 'webmaster', David Bradley as he has a frame on his Alpine.
I have a feeling that there are some doubts about the legality of towing in this way - but it's up to you to check.

I happened to pick up a Haynes' manual on trailers, which confirms my suggestion that towing with an A frame is only legal for recovery of a broken down vehicle. I have never heard of anyone being stopeed and prosecuted, but you should check for yourself.

I understand you can use an A frame for recovery only. If you want to tow a car (say behind a motorhome) then the A frame must be able to brake the towed vehicle. They are available for about £800!

I found this on the website of the National Trailer and Towing Association:

Q. I have a motor home and want to tow a Fiat Seicento behind it using an A-frame. This car has a kerb weight under 750 kg so am I legal with this outfit?
A. Sorry no is the answer. The law regards this as an unbraked trailer and you are allowed to tow up to 750 kg Gross Trailer Weight, not a car’s kerb weight. The figure you have to use is the car’s Gross Vehicle Weight or Maximum Permitted Weight. This is usually at least 300 - 400 kg more than the kerb weight. We have no knowledge of any car sold in the UK that has a GVW under 750 kg. The only vehicle we know that is completely legal to tow with an A-frame is the French Aixam small "car". This is a full four seater and details can be obtained from Aixam UK on 01926 886100. An A-frame or dolly can only be used to recover a broken down vehicle to a place of safety. Transporting a car is, therefore, illegal. A-frames may be offered with a braking system that applies the car's brakes. These do not conform to the law as the car then becomes a "braked trailer" and has to conform to European Directives contained within the Construction and Use Regulations. It does not conform to the European Directive 71/320/EEC and amendments regarding braking requirements in any way. The use of this A-frame for transportation is illegal. It is still OK for use to recover a vehicle to a place of safety.

But it is true that there are suppliers of A frames which provide a connection to the towed car's braking system.