UK (not US) foreign tax exclusion

I have moved to the UK and consider myself to be a permanent resident. I am married to a UK citizen, have a job in the UK, and plan to eventually obtain UK citizenship. I consider my domicile to be the UK.

I know that I am entitled to take a foreign tax exclusion for my UK job income when I file my US taxes.

However, in the US, I have uncashed savings bonds, which are currently worth a substantial amount.  They are jointly held with my mother and are currently in her possession.  If I cash them, will I have to pay double tax, to both the IRS and Inland Revenue, or does Inland Revenue have a similar foreign tax exclusion for income earned in the US?

Your domicile is a matter of choice, not fact.  If you intend to stay here the rest of your life, then you are domiciled here.  If you intend to return to the US when you retire, then your domicile is the US.  No one can prove what your intentions are, they are in your heart only.

If you are domciled in the UK, the IRS will tax them at some small rate (15 - 28%), and the UK will tax them at 40%, less any US tax paid.

If you are NOT domiciled in the UK, the IRS will tax them at the small rate and the UK will tax them only if you remit the proceeds to the UK.  There are ways to remove the remittance tax which are too complicated to go into in a short space.

It is your choice where you wish to spend your retirement years.  If you choose the US, you can always change your mind later on when you actually hit retirement age and choose the UK. 

Depending on the tax savings, you might wish to carefully consider where you intend to retire.