Some Contract notes for those who need it. It is good revision for me too, to see how much I can remember. This is only for the substantive, advanced information topics (Consideration, ITCLR, Frustration, Consumer Rights Act 2015, Remedies)
Consideration
Consideration is something of value each party offers in exchange; historically, this element was required as part of a contract to create evidence of an ITCLR, however, it still stands as crucial today. It can be money or an act/omission, amongst other things. It need not be 'adequate' but must be 'sufficient' (Thomas v Thomas) in the court's eyes; this essentially means that it must have some genuine inherent value, but whether or not it is a 'good' or 'bad' deal is not the business of the court. This is the fundamental rule of consideration, these are the others:
Past consideration is not valid consideration: Past consideration is not sufficient (Re Mcardle); 'past' refers to it being executed prior to contract formation. For example, if A promises to give B a car and later B promises to give A £100 for this car, this £100 is not enforceable consideration because it was formed after the promise to pay the car (the past consideration). However, there are exceptions to this rule. If it is implied that someone will receive monetary payment for their efforts, this may arise an instance where past consideration is valid ( Lampleigh v Braithwaite, Re Caseys Patent).
Previous contractual obligations cannot form new considerations: As proven in Stilk v Myrick - existing duties cannot provide new consideration. This also applied to obligations under statutory authority (i.e. legal obligations, such as those held by a police officer) as shown in Collins v Godfrey. There is an exception to this rule when the performance of existing duties (e.g. say the same duties but now in a narrower time frame) can be new consideration, really it is up for the court to decide (Williams v Roffrey Bros & Nicholls)
Consideration must move from the promise: Essentially just privity of contract. A third party cannot enforce consideration (Tweedle v Atkinson). There can be exceptions to this under The 'Contracts (Rights of a Third Party) Act 1999 - for example, when a contract confers benefit onto a third party or a contract explicitly states an identified third party by name or description.
The performance of an existing contractual duty for a third party can provide new consideration: Scotsen v Pegg. I think Shanklin Piers v Detel is also relevant here in terms of collateral contracts. Both of these cases are more to do with the privity of contract than consideration so I wouldn't stress too much over them.
(I forgot something - the promise or acceptance of part payment of a pre-existing debt in place of the whole amount is NOT valid consideration, as show in Foakes v Beer.)