A copy of a will (rather than the original) can be submitted to the Probate Registry and an oath sworn regarding the consequences of whether the will is accepted or not.
If the Probate Registry is convinced that the photocopy is definitely a true copy of the most recently made will (and that the original wasn't revoked by the testator, e.g. through destruction) then probate may be granted as normal.
If there is doubt about the will, the Probate Registry may direct that it can only be accepted if all of those affected by it (i.e. its beneficiaries and anyone who would lose out through the intestacy rules not being applied) give their consent to it being accepted.
If that stage is reached, but one or more of those people affected by the will refuse to agree to it being accepted, a court hearing might be required to make a final decision.
The date upon when the will was written, together with the date upon which your uncle collected his will from the solicitor, might well be considered relevant by the Probate Registry and/or court.
For example, if he wrote his will in 2010 and withdrew it from his solicitor's safekeeping in January 2016, a court might well think it likely that he intended to revoke it (either by destroying it or by making a new will). So a photocopy of his 2010 will might not carry very much weight. However a photocopy of a will written in February 2016 would be more likely to be be seen as reflecting your uncle's last wishes.
As a first step, I suggest establishing who would benefit from your uncle's estate if the intestacy rules were to be applied:
https://www.gov.uk/inherits-someone-dies-without-will
If the position turns out to be no different from that if the will were to be accepted, then you should have no problems with the Probate Registry.
If the intestacy rules and the application of the will's provisions would lead to different distributions of your uncle's estate, you should find out if everyone who would gain or lose is prepared to consent to the will standing. Again, you shouldn't have too many problems if that's so.
However if there's likely to be a dispute it's definitely time to consult a solicitor!